1. Is the hard drive full?
2. Are you trying to save a PSD? If s o then if the files are over 2GB each, Photoshop can’t save as PSD.
3, Do the filenames have any of these characters? The Adobe plugins API can’t save files with these characters in the name.
4. Are yo trying to save to a local drive, external drive, or a cloud drive? Often PS blocks plugins from saving to the cloud. For testing, have you tried saving to a folder on the desktop?