So, an update: I changed my password in my dashboard and then the Wayfarer app unlocked.
I would like however someone from Niantic to tell me if the problem was that I connected to the same account from a different device (and did not sign out when closing the app)
While the connection may fail due to network issues, it should not cause any issues to login with another device as you have done. There is a certain timeout period if the Lightship endpoint is not responding that may have occurred at the time you tried to connect.
If you experience this issue again in the future, we could investigate further if you provide us with your email and the day/time the issue occurred.