All of a sudden I've been working on files & saving as PSD but when I go to reopen I am getting a message that says ...could not complete request because it is not the right kind of document. I can save the same file as a JPEG. What can I do to open these files?
Could you have misnamed the files and they are actually too or psb?
What have you done for trouble-shooting so far?
Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:
https://helpx.adobe.com/photoshop/kb/basic-trouble-shooting-steps.html