Save for web error - Mac OS Catalina

I recently had this same problem. I couldn't save for web on certain files, but it worked for other files so I knew it wasn't an OS issue. I tried restarting, checked the image size and none of that worked. I then gave Photoshop Accessibility in Security & Privacy and still that didn't work. What worked for me was going into my Preferences -- Adobe Photoshop (Year) Preference Settings and deleting 'Save for Web Prefs.psp' and also deleting Preferences -- Adobe Save for Web 13.0 Prefs. Restart and tried saving again and it was successful.

Hope this helps someone.

The way I resolved this issue for a user was to provide full disk access to photoshop - No error

GIF animated perfectely fine. 

I just had this same issue happen for the past two weeks. My friend walked me through it. I recently signed up for Dropbox Backup and apparently that was the issue. I had to disconnect Dropbox Backup to make my Photoshop work correctly. 

Grateful we found the problem, but WHAT THE HECK. How annoying. 

Here's what worked for me. 

When exporting, check your image size. You can see below that my pixel width was 8192. I needed to make the pixel size smaller. I kept the same proportions  (Keep the chain icon locked), and lowered it to 4,000 (pictured below as well).

The error message disappeared and I got my gif!

Hope this helps. 

The reason we've heard no answer from Adobe is that Adobe, CreativeCloud, and its dozens of hidden "helper" apps get more and more intrusive into your system with each passing year. Apple introduced a lot of privacy and system sandboxing features with Catalina, and now Adobe doesn't want to spend time getting "Save for Web" to work again without relenting on some of those system intrusions. It's easier for them to just call it "legacy", even though hundreds and thousands of people still rely on that functionality.

The only solution that was successfull for me, is keeping a 2019 version of Photoshop just for the sake of exporting from "Save as".

I uninstalled the latest version of Photoshop and then istalled an older one instead. It's now working. I'm on a Mac and was on the up to date version for March 24th 2021...  on the current version of Big Sur.

I also experience this problem and I can't find a solution to fix it:

macOS Big Sur 11.1 (20C69)

Adobe PS 22.1.1.

Does anybody know the solution to my problem?

The Same problem. Last version Big Sur and PS 2021. 
Didn't save web GIF.
No more dollars for Adobe company from my side. 

I, too, am getting this error. Funny, it worked this morning, and didn't this afternoon. Really threw a wrench into my Christmas get out of the office early! I did the Photopea workaround which was fine, but not what I want to keep doing! BTW, I am up to date on everything. What is going on???