Tried to refresh Firefox, but it failed to restart
I tried to refresh the Firefox browser as recommended, as it's been running slow. However, I wasn't sure that anything was happening and, as it didn't restart after half an hour, I Force Quit it and found that it appeared to be the same as before. I don't really know whether it was refreshed or failed to do so, as I don't know what to look for. Should I try again? I can send the Crash Report which has been sent to Apple, if that helps (I copied it before it was sent). I am running Firefox Quantum 60.0b12 on Mac OS Sierra 10.12.6.
You can create a new profile to test if your current profile is causing the problem.
See "Creating a profile":
If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.