Are you opening Firefox from the application directory or the mounted install disk (that's stored on your desktop)?

This thread had this as the solution, which I believe is the exact same issue you're having:

Just to check that I understand what's happening here, is this an accurate description of what you're seeing?

1. When you launch Firefox, it is not signed in to your Firefox Account, and it does not have any of your saved bookmarks, passwords or preferences.
2. You sign in with your Firefox Account and the bookmarks, passwords etc appear after syncing from the Account.
3. When you exit Firefox and launch it again, you find that it has forgotten the above and you have to sign in once again.

One possible cause of this, is if you are running Firefox directly from the downloaded disk image rather than copying it locally to your computer. You can check this by opening a new tab in Firefox and entering "about:support" in the URL. This should bring up a page with some diagnostic information about your local Firefox install, one of which is labelled "Application Binary". Does the value for "Application Binary" change every time you exit and re-launch Firefox, or does it stay the same?

Let me know!

That was the solve! Thank you!

I don't know how I didn't come across that thread in my searches for a solution, but I appreciate you linking it and taking the time to address my concern.

how do you uninstall application binary? Can't save passwords.