It can occur that you cannot add a printer of the printer list to a cluster.
What to do
Check if the printer is part of another cluster and shares the same synchronisation areas across the clusters.
The printer can have newly installed printer software. In the cloud service administration portal, first remove the printer and then register the printer again.
Your Service organisation makes the PRISMAsync Remote Match licence available in On Remote Server (ORS). This licence is based on the serial number of the printer.