Save For Web error Photoshop 21.1.2 macOS

Hi,

My Photoshop version is 21.1.2 and my operating system is masOS Catalina 10.15.4 

I am trying to export and compress gifs using the Save for Web (Legacy) dialog and repeatedly get this error when I hit save, no matter what the export settings are, what the file size is etc.

I have tried resetting my Photoshop preferences, I have also tried resetting my macs PRAM.

I was getting this error sometimes before the most recent photoshop update, but now I get it everytime.

I am seeing a lot of other posts about this problem but none of these solutions are working for me!