This host is
This host: Primary - Standby
which means that this is not the active device in the network.
Since changes are always replicated from Active device to standby device and not from standby device to active device;
Whenever you try to make any changes on the standby device the error message that you got appears.
To correct this situation you must logon to "Secondary - Active" device and make the required changes.
Once the changes have been made save the configuration.
Sachin