License server error 500

[Hayden]

Hi Simon,
I've just had to set-up my QNAP nas again. I'm having trouble entering the licence details.
This is what I see in MinimServer:

License server error 500: [6b15fdae] Incorrect license type 4; resetting to Starter Edition
License server error 500: [6b5fb537] Incorrect license type 4

Just to add, I did try deleting the license files as above and restarting, but with no luck.
Please help!
Kind regards
Hayden