How can I unlock (in Basecamp) the City Navigator Europe NTU 2021.3 map update I've just installed on my Zumo 590 and Windows PC?

I have downloaded and installed the  City Navigator Europe NTU 2021.3 map update to my Windows PC and my Garmin 590LM. 

When I open Basecamp, the map shows as locked.

What do I need to do to unlock it please - as the browser based unlock method is no longer available?

Many thanks.