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 synchronization 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 organization makes the PRISMAsync Remote Match license available in On Remote Server (ORS). This license is based on the serial number of the printer.