AWS Connect: telephone number not in use when calling

I've got a phone number claimed via AWS Connect. I used it for about a year. However it doesn't work anymore while nothing has changed. It's still listed in the phone numbers page with the correct contact flow. When I call the number the carrier says "the telephone number is not in use" in my own language. This happens also with one of the AWS example flows attached to it, so the problem isn't related to my flow. I've looked through the other options like hours of operation, but it all seems fine. There's not much to configure that could go wrong and I start to suspect the problem is AWS-carrier related.

I don't have technical support for this account, so I hope somebody can help me out. According to the AWS status page there are no issues with the service. I'm running the instance in Frankfurt EU.