@YAQUE Sounds as though you've tried a lot of things already. Is this happening on any and all files you try to save for web? If it's isolated to only a certain batch of images, is it possible the files have a lock on them? If you roll back to an earlier version do you still have the problem?
Okay. In your systems preferences (Security and Privacy), does Photoshop have Full Disc Access? Write permission errors usually have something to do with how your admin/user privileges are set in your system.