Sometimes, there are differences between the Bitwarden apps downloaded from the Mac App Store vs. those downloaded directly from Bitwarden. You could try downloading from the location you didn’t use previously and reinstalling.
Also, although I have not seen this particular issue on GitHub, there are several reports of biometrics issues experienced by users who have multiple Bitwarden accounts (and use account switching on their Desktop app). Is this the case for you?
From what i remember the biometrics only work if installed from the App Store. Again, it works on Chrome for the same macbook, but not on FF. I have a single Bitwarden account.