Greasemonkey 4 has broken the old userscript API used for decades. You can read more about it in their documentation and then rewrite the affected parts. A simple solution is to use Tampermonkey or an older GM.
@wOxxOm ironically, this script don't use script manager's API at all. Problems have to be more complex.
javlibrary enchancer not working on new greasemonkey
Hello, I recently migrated to FF quantum and noticed that the script no longer works, before it colored the entries on the site by the status of my account, owned green, watched gray etc. but it does not do it anymore, could somebody please take a look and see what is wrong? It works ok on an old FF with older version of greasemonkey though so it is not a problem with the site.