Not sure; I’ve tried interrupting the login and this does not produce the expected error message either. I do see that the Vipps session cookie is set, and that one reaches the “my account” page from the “vipps login” handler, so my first guess would be that the “my account” page for some reason is cached. I see you are using cloudflare for this, could you try to ensure that the “my account” page is exempted from caching? (Also all pages that start with /wp-vipps-login/, even though it seems this was *not* cached)
Also, when completing the login process, have you checked that the user isn’t created in the database? It may have succeeded in this but not in logging in the new user.
There may be some sort of error message logged (which, since you are using Woo here, should be in the Woocommerce/status/logs screen as “login-with-vipps”, but at first glance it looks like too much caching.
Is it OK if I try to actually register a user to see what happens?
