Partially Installed - akeeba/onthos GitHub Wiki

One or more of the files and/or directories of the extension, as declared in its XML manifest, are missing.

Why is it a problem?

If some files needed by the extension are missing, the extension will malfunction, or may not work at all. In extreme cases it may cause complete inability to access your site.

Suggested fix

You will need to reinstall the extension to make sure the missing files are installed back into your site.

It is recommended that you install the package which contains the extension twice in a row, without uninstalling it before or in between.

Notes

Whether the extension is actually partially installed greatly depends on the accuracy of the XML manifest. It is possible that someone or something edited the XML manifest in a way that made it no longer accurate.

As to how you could truly end with a partially installed extension, the simple explanation is that someone or something deleted files. We've seen it all. People messing around with extensions. Moving sites from Windows / macOS to a Linux server with detrimental effect to the capitalisation of folders (e.g. FooBarModel vs fooBarmodel; did you catch the two letters with switched case which don't matter on Windows / macOS but will cause problems on Linux?). Server issues causing lost files. Bad automation. Do not assume that just because you don't remember doing it, and you don't assume anyone else did it that you were hacked. Real malicious actors don't break your sites; they surreptitiously install code to subvert data, or have your site do their bidding without causing any visible damage which would lead to discovery of their malicious additions to your site. In short: if you think the extension is broken because you were hacked, it is extremely unlikely you are right.