Trados Studio 19 asking for Activation code although it was activated long ago

Have not used my copy of Trados Studio 19 for at least a year. Went to fire it up on a laptop I have bought in the interim and a window pops up asking me for an Activation code. I tried putting the code in from my SDL account page, but it is rejected.

Why can't I open Trados Studio 19, and what do I need to do to regain access to something I have already paid for?