I have the same issue. Bought 1 month. Shows as Complete. Money went out from my bank account, and account page reports my account is Active. But, login app says Subscription expired. Have a ticket open, but no response as of yet.
And I also have a 2d problem to add to this now… no clue if they are related or if I’m just really unlucky! But, the Battle.net app now says an update is needed but it keeps crashing at 98% no matter what I do.
UPDATE
2d problem, related or not, but managed to solve this part due to this post:
FIX - Endless Scan & Repair loop - Support / Technical Support - World of Warcraft Forums (blizzard.com)
And still stuck at Subscription expired!