AppSync can't connect to Cognito in eu-north-1

Hello AWS re:Post

I have an AppSync API and a Cognito userpool in the region eu-north-1. Until last week, I've been authenticating my queries with the cognito pool. One day last week, I wake up and it doesn't work in the AppSync GUI. When I go to the API settings, it doesn't show any userpools for the selected region (eu-north-1). If I select another region and switch back to eu-north-1, I get an error message saying "Error: Network Failure" as seen on below screenshot: I've tried the following things so far:

Make a new cognito pool in eu-north-1 -> Doesn't work, can't see new pool either

Make a new cognito pool in another region -> Works, can see this pool, but my stack and domains are set up on eu-north-1

Make a new AppSync API in eu-north-1 -> Doesn't work, still same error

Make new AppSync API in another region -> Doesn't work, still same error

This error has me stumbled. What can I possibly be doing wrong to get this result? Is there a connectivity problem between AppSync and Cognito on eu-north-1? At first (after the GUI problem appeared), I was still able to make queries to the API from external programs, authenticating with the cognito pool, but this obviously stopped working as soon as I started testing with other Cognito Pools since I have no way of selecting the original again.

Let me know if I can provide any other relevant information

Best regards, Alexander