My first PEz was like that.
If I held the connection into the PEz
just right, I could get it to work.
See:
https://www.mobileread.com/forums/showthread.php?t=56391
Also look at Message #35 of that post for what I found would make it work on a problem machine.

The downside to that
fix, is you disable USB2 mode that you might need (for speed) if you use USB Mass Storage devices for large files.