Hi I noticed that one of my add-ons were not working anymore. I tried to reinstall it, but got an error message. "The add-on downloaded from this site could not be installed because it appears to be corrupt." I then noticed that none of my add-ons were working except for the language pack and Lightning. I assumed I had a corrupt file in my profile folder. First I deleted the '''extensions.json''' file . That did not help. I wanted to clean up. I uninstalled all extensions. Then I deleted the following files and folders: '''addons.json''', '''addonStartup.json.lz4''', '''extensions.json''', '''extension-settings.json''', '''extensions''' and '''extension-store'''. That changed the default language of the GUI. When I try to add a language to Thunderbird I get the following error message: "Thunderbird can’t update your languages right now. Check that you are connected to the internet or try again". I Still can't install any add-ons. 78.14.0 (64-bit) on Linux Mint