Why am I getting the Stream Desktop "Activate" prompt again?

The Stream enabled Desktop applications and Streaming Services Web app use the Network card’s physical address (MAC) as its method of recognizing an Activated PC.

If the PC, on which you have SubC Stream enabled desktop applications installed, has more than one Network card (NIC), and the Stream desktop application happens to connect to the Streaming Service via a network card that has not been activated, you can simply activate that NIC also with your SubC Streaming Service Group.