Which version of macOS are you using?
I use version 11.3.1
If you go to Apple>System Preferences>Security & Privacy>Privacy>Full Disk Access and add Photoshop Elements 2021 (/Applications/Adobe Photoshop Elements 2021/Support Files/Adobe Photoshop Elements Editor.app) does that fix the issue?
I did it but, unfortunately, it doesn't fix the problem.
Does your mac have an Intel or Apple M1 proceesor?
You can tell by going to Apple>About This Mac
See if restarting your Mac makes any difference.
Unfortunately, no difference.
Is your photoshop elements 2021 from the Mac App Store?
I always have the same problem. It's not solved. thanks to help me until I we fix it.
If you open an image that just has a simple file name like test and then the extension, for example, test.jpg, does that make any difference?
I did it and tried to export for the web with this name : test1.jpg
But it's not working.
I have installed again the OS. No positive result. Always the same problem.
Unfortunately, this appears to be a known issue with the Mac App Store version of Adobe Photoshop Elements 2021 and Adobe are aware of the issue and working on a fix.
The Mac App Store (and Windows Store) versions of Photoshop Elements 2021 are separate builds from the standard versions and also have their own independent update cycles. As such, I can't give you any indication on how long it might be before this issue is addressed.
In the meantime. the only workaround I can suggest is to use the standard File > Save As... menu option, then choose whichever image format you want to output for the web in the Save as type: field, e.g. GIF, JPEG or PNG. You still get a range of options to choose from (depending on which image format you select), albeit slightly less than you would in the Save for Web dialog window. But you will need to resize your images before saving if you usually do that step as part of the Save for Web process.
Hope that helps.
Good catch Phil!