Unfortunately I cannot get it to work for Photo 2 by logging in (once logged in for 1 app, I'm logged in for all) nor restart or reinstall.
The link for Designer 2 is fine, maybe because I "bought" the trial first?
Anyway, I will wait for the next update and hope it'll fix it. No hurry!
EDIT:
Okay, I tried a little bit more and got it now: I deactivated the licenses on my iPad for all the apps and re-activated them by storing the purchase and logging into my account in the window showing immediately after the purchase window. The apps are now all showing in the Affinity Store (which was not the case before) and Studio Link works.