You can check the read/write permissions and ownership of files and folders in both main/root and cache locations and possibly remove the Mozilla/Firefox folder.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
• https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

My problem is not starting Firefox. I can get it running. Its recovering missing bookmarks and bookmarks toolbar. Is that data still accessible or have I permanently lost it?

Copied mac Firefox profile and tried to load profile on newer mac os partition.

Are you going from one mac to another mac or just a new partition on the same old mac? What OS version?

I'm going from a imac partition wih os Sierra to a partition with os Monterrey. I have a bookmark save from 5 years ago but nothing since. Is the latest bookmarks and bookmark toolbar accessible somewheres or is it lost forever?

Note that you need to copy profiles.ini as well as this file stores the profile registry data.

• https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

If you copied a profile then check that you are the owner and have read/write access in both profile locations.

• PRIMARY: ~/Library/Application Support/Firefox/Profiles/
• SECONDARY: ~/Library/Caches/Firefox/Profiles/
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data