Hi, I'm not familiar with Linux specifically, but have a look through Firefox won't start - find solutions.

This can sometimes happen when a security program/AV blocks it.

You could also see if it will start in Safe Mode Diagnose Firefox issues using Troubleshoot Mode.

This might be of some help Install Firefox on Linux.

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

Hi, please check the output when you use the commandline to run Firefox

command: firefox

As Scribe said above, you may want to use safemode

command: firefox --safe-mode

Firefox tends to dislike when 2 separate firefox instances are running, so maybe kill firefox or restart your computer

command: killall firefox

If these don't solve your issue, have you tried reinstalling firefox

command: sudo apt remove firefox && sudo apt update && sudo apt install firefox

Thank you, Andmagdo