Can't add external SSD on MacOS as Scratch Disk for Photoshop

[aimee93]

I have an external SSD formated as exFAT. My mac software is up to date as is Photoshop. The SSD doesn't come up as a scratch disk option with Photoshop but I've used it sucessfully as one with Illustrator and After Effects. I've tried resetting my Photoshop preferences and tried to see the SSD settings to see if permissions need changing but they seem okay. I'm not great with the technical side of things, is there something I'm missing? Has anyone has success resolving this problem? 

[D Fosse]

exFAT doesn't work well with Catalina. New Apple policy. Lots of people have different problems with it. Use APFS or Mac OS Extended.

[aimee93]

Does this mean buying a new SSD or can I reformat my current one from exFAT to APFS?