So awhile back I’d installed add-on called Wikitree Sourcer. then noticed that any time I installed new add-on, such as FoxyTab I would not see the add-on name but instead now see then all with name “_MSG_extensionName” and icon is “[1]”, and opens the Wikitree Sourcer add-on. I tried removing all extensions, then adding only FoxyTab add-on but still installed it with name MSG_extensionName and started Wikitree Sourcer add-on. How can I fix this so they go back to installing correctly?
Hey @Catherine_Spry! Welcome to the Add-ons section of Mozilla’s Discourse server 
This is the first time I’ve heard about this kind of issue. In order to help investigate this issue, could you share some screenshots where __MSG_extensionName__ or similar text appears in Firefox’s UI? Also, can you clarify whether this issue happening with all other extensions or just FoxyTab?
When (date or Firefox version number) did this start happening?
Also, it would help if you could visit about:support and DM me a copy of the data on that page.