Why do I need to press the program button to upload - TeensyUser/doc GitHub Wiki
Usually you don't need to press the program button if you use the stock Teensy uploader or external uploaders like TyTools. Here some trouble shooting recommendations:
Generally
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Make sure you don't have 'No-USB' selected in the USB-Type options. With this setting your Teensy does not appear on the USB bus and can not be reprogrammed without pressing the button.
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Make sure you don't have another uploader or any other program grabbing the port running in the background. E.g. if you normally use TyCommander and have Teensy.exe running in the background, Teensy.exe will detect a changed firmware and starts uploading it immediately which blocks TyCommander from accessing the board of course.
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Make sure your sketch doesn't crash the USB Stack. To check, press the button and upload a known good sketch (e.g. blink.ino). If, after you uploaded blink.ino, uploading works without button, it is likely that something is wrong with your sketch.
Windows
- Uninstall ALL serial and ALL HID ports that are not active to get rid of screwed-up ports. (Obviously with Teensy disconnected). See here for details.
Win7 specifics
- If you set the USB-Type to 'Serial' you need to make sure to have the Serial driver installed (https://www.pjrc.com/teensy/td_download.html). Otherwise, the uploader can not switch your Teensy to bootloader mode. If you don't want to install the driver you need to choose any other USB-Type to allow uploading without pressing the button.