Hi stitch, welcome to Mobileread! I responded to someone else a little while ago about this same problem (only it turned he didn't have this problem).
Check out this thread:
https://www.mobileread.com/forums/showthread.php?t=43858. Post #5 says "I had to press the reset button for 10 seconds, then volume + & bookmark button for one minute and that resets the drm in the unit."
Then of course you need to authorize it with your account.
Let me know if this works for you. Otherwise I guess you will have to call Sony support.
I believe someone posted a few days ago that you can now have 6 devices and 6 computers authorized.