• I don't have sounds
• I'm missing images for some cards
• "Application failed to initiate correctly (0xc000001d)"
• "Not a valid Win32 application (0xc000007b)"
• "This app can't run on your PC"
• "Unspecified" or "Windows Update" error (0x80240017)
• Avast Antivirus is flagging Cockatrice as a potential threat
• Avast antivirus causes images to stop downloading
• "Unknown Error: -1" message upon login
• "Missing Features" error upon login
• "Socket Error: xxx" error messages explained
• Cockatrice crashes when I try to save or load a deck
• Cockatrice can't load my gtk theme
• Menus are not visible on Ubuntu 14.04 when not using Unity
• I have problems with the Interface, some parts/widgets are missing!
• How do I uninstall Cockatrice and all settings (Mac OS X)
• I have problems with updating Cockatrice
• I own a very old PC and need a 32bit copy of Cockatrice - Where can I download it?
• I own a very old PC with Windows XP - Where can I download a compatible version?

Check your settings. Make sure that sounds are enabled. If enabled, check that the sound file location setting is correct. If it's not correct, check for the sound files under Program Files/Cockatrice (on Windows).

On Ubuntu, make sure you have both libqt5multimedia5 and libqt5multimedia5-plugins installed.

Please ensure that you have recently updated your card database to have the most recent images available.

You may also need to go to Settings → Card Sources then Delete Downloaded Images and restart your client to do a fresh download of all image files.

Please also be aware that some cards (especially tokens) do not have officially printed art at all and so may not have art in Cockatrice. Check Scryfall to make sure that card art exists before reporting an issue.

This can be caused by anti malware applications preventing the Cockatrice program from running. If you have a program such as Malware Bytes, verify that the Cockatrice application is not being blocked from running by your malware software.

On Windows 10 the message might be "This app can't run on your PC"

This is a generic error stating that something went wrong when trying to load Cockatrice or one of the libraries it depends on.

If you're still running an old 32bit version of Windows, the problem could be caused by the fact that you downloaded and tried to run the 64bit version of Cockatrice.
Check this link (https://support.microsoft.com/en-us/kb/827218) to make sure which version of windows you're running and that the Cockatrice setup file is matching accordingly:

32bit Windows → Cockatrice(...)-win32.exe
64bit Windows → Cockatrice(...)-win64.exe

Where to download Cockatrice (32bit)

See this question and it's replies in the Microsoft community.

The Oracle tool incorporates the zlib libraries to handle zip files. At some point someone submitted a profile to avast that also included the zlib libraries, and now anything that uses those same libraries will show as infected, because the zlib dlls will be flagged.

Some users that run Avast antivirus report that Cockatrice stops downloading images. Avast seems to prevent Cockatrice from saving downloaded images, changing Avast's settings or disabling it should help. Users have also reported that the portable install option on the Windows installer avoids this issue. To fix, follow these steps:

1. Open the Avast Antivirus app.
2. Select 'Menu' in the top right. Select 'Settings' in resulting drop-down menu.
3. Select the 'General' tab, then select 'Exceptions'.
4. Click 'Add Exception'. Select 'Browse' and navigate to your broadest Cockatrice folder, check off that folder, and hit 'OK'. Repeat this step for each folder location containing Cockatrice files.
5. Reload Cockatrice, and you should be able to download card images once more.

This message can be caused by one of two things:

• Your Cockatrice client is out of date
  The server you are trying to connect with is requiring you to have a newer Cockatrice client, but your client is too old to understand that, and instead displays the Error: -1 message.
  In this case, you need to update your client.

• The server supports max user limits, but your client doesn't
  The server is trying to tell your client that the maximum user limit has been reached, but your client doesn't understand the message, and displays the Error: -1 message.
  This will no longer occur in the next release of Cockatrice.

The owner of the server you are trying to connect with is requiring a set of features your client does not have. In order to connect you will need to upgrade your client. To upgrade, download the most recent client. Close the current client you have and backup your deck files. Run the installer for the new client and install the client as you did when originally installing the application.

Socket Error: Connection timed out or Socket Error: Host not found
First make sure that you entered all server information correctly. Match the data with our Public Servers list, especially host name/address and port! You can also check if there are any known issues with the server at the moment on the linked server pages, additionally you should check out the server statistics or up time and the server administrator tweets for announcements for example.
Furthermore you should make sure that the server name is resolving to the proper IP address to see if there are any problems with your DNS resolution. From there work your way down the connection path. For example, next check that you don't have any type of firewall or malware type product preventing inbound/outbound connections to the server your trying to connect to. Next make sure you're not behind any type of proxy or firewall outside your personal PC or home network. Many places such as schools or work facilities have proxies that prevent lots of port connections outside the usual 80/443 type ports. If that's the case you can try a server which offers connection abilities on these ports.

This is caused in one of two ways.

First: another program is adding an extension to explorer and those are messing up with Qt. Known offenders are:

• The "Dell Backup and Recovery" software installed on most DELL pcs (source)
• Some versions of Dropbox (source)
• Some versions of "Git" (source)

If this is the case, try uninstalling or installing a newer version of the software.

Second: can you try to:

• Close cockatrice
• Browse to Cockatrice's installation folder (Usually C:\Program Files\Cockatrice or C:\Program Files (x86)\Cockatrice)
• Rename cockatrice.exe to cockatrice2.exe
• Double click on it in order to run it
• Test if deck loading is working. If this fixes your problem, it's due to some internal windows black magic (source)

The issue is apparently solved if libgnome package is installed in your system, but there's a way to fix this without having to install it. Edit your ~/.config/Trolltech.conf file and add the following lines

[Qt]
style=GTK+

Cockatrice is able to load both gtk2 and gtk3 themes.

The package appmenu-qt5 attempts to make the menus of Qt programs fit with Unity. This causes problems with non-Unity environments. Removing the package fixes the problem:

sudo apt-get remove appmenu-qt5

Try to select View → Reset layout in the menu, it will bring back all disabled widgets at their default positions!

Provided you did not change the default locations, you can delete the following directories/files:

/Applications/Cockatrice.app
/Applications/Oracle.app
~/Library/Application Support/Cockatrice/Cockatrice
~/Library/Preferences/com.cockatrice.cockatrice.plist
~/Library/Preferences/com.cockatrice.oracle.plist
~/Library/Preferences/de.cockatrice.Cockatrice.plist
~/Library/Saved Application State/com.cockatrice.cockatrice.savedState
~/Library/Saved Application State/com.cockatrice.oracle.savedState

Because of prior implementations of the client update system, it took a couple revisions before we settled on the client update mechanism in place today. That means that older clients may not update properly because they rely on code which no longer functions as expected or download links that no longer exist. Please download and install the latest release manually.
Once this is installed, you can update your client in the future through the normal process:
Help → Check for Client Updates

Note: The updater only works on Windows and macOS due to generally different update policies on Linux.

Because all modern PC's can run 64bit applications for years now, we default the link on our website to the version over 95% of players use on Windows. If you happen to run on old hardware/operating system and your combination is still dependent on 32bit only, we have you covered though!
Check the Downloads section of our most recent release here and download the win32 installer of Cockatrice.

A more detailed and technical explanation of why we have to switch to 64bit can be found on reddit.

The last compatible Cockatrice version with Windows XP is v2.3.17. You have to download the 32bit version!

Since July 2018 the major servers require Cockatrice 2.6.1 though, so you wouldn't be able to connect to a server with such an old, unsupported and unsafe operating system.