Okay I got it working, to help out others try as I did.
Go to your Xbox 360 settings, then storage / hard drive (were the app is installed) / Games and apps.
Now once you're in there you will see 3 Plex installs.
The 121MB main app install and 2 other small ones. Delete the two small installs, 64kb and 60kb.
That is where App Cash is stored and for some reason it's interfering with the new server updates and such.
After deleting both of those I had no trouble using the app running the newest PMS. The error is GONE!
Hope this helps someone
Happy New Year
Does not work for me. Got latest server 9.11.12 installed on my Qnap arm.
