When I click on a link (in an email) I get this pop-up error message

Close Firefox. Firefox is already running, but is not responding. To use Firefox, you must first close the exiting Firefox process, restrt your device, or use a different Profile.

I do have Librewolf (in Settings) as my Default browser and have removed Firefox from my software lists. It would seem that the links are thinking that Librewolf IS Firefox? When I click on Librewolf Support (in its settings) I end up at a page on Mozilla for Firefox. Any thoughts/suggestions? [I am currently using Zorin OS]

Does Librewolf have/want ‘bug reports’?