cannot receive new updates because System Update entitlement

Hello

I am getting since some days the following error message in ZCC / Configuration / System Updates:

You cannot receive new updates because System Update entitlement has either expired, or could not successfully authorize to NCC. If the error persists, configure the entitlement later with a valid activation code.

Is there a know error with NCC? My ZEN 11 is still activated. I have no idea where the problem is....

Regards
Andreas