That most likely the Interfaceif index changed on the device it self. / Or the Interfaces were removed from the device and no longer available under the Device .
Settings > Manage Nodes > Select the Node > Expand > Select the "Unknown" Interfaces > Delete . Once Done.
(Please Note . by deleting the Unknown interfaces you will loss the historical data for this interface )
Go back to the Node details page > Do "List Resources " > select the interfaces you wish to monitor .