I had this problem too.
Try these things.
Click the top/first font on the list of "All Fonts".
Go to the bottom, hold shift and click the last font to select them all.
Click file ---> Validate Font.
This checks all your fonts for problems, delete the severe ones.
If that doesn't work click Edit ---> Resolve Duplicates.
Those were the first two things I tried. If they don't work you need to restore all your fonts to the defaults.
I was lucky enough to have a time machine backup so I could go back and restore the font folders.
Maybe someone can upload the default font folders.
Contact me if you still need help and I can upload the default fonts so you can restore.
Hope this helps!