A single-user license does not allow for a distant use sharing a screen following the remote desktop operation type. It is only the network license that provides this possibility.
If you are using an RFEM/RSTAB license and want to activate an add-on module for a 90-day trial, all you have to do is to start this product in Project Navigator – Data or by using the Add-on Modules menu.
This error message informs you about the impossibility to activate the add-on module using Remote Desktop on the PC with the RFEM/RSTAB license. It is necessary to switch to local use to activate it.