This is a known issue (since some days) and is currently under investigation. This is not caused by changes in our code bity seems to result from changes on Amazon’s side.
The first try to fix was not successful, so please be patient.
@J-N-K
I was able to get this working now.
I updated to the 2.5.7 unstable (not 100% sure if that is necessary or not)
Removed Amazon Account Thing and any other echo/amazon things related.
Uninstalled the binding (not 100% sure it is necessary)
Added binding back.
Then did http://myIP:myPort/amazonechocontrol/ and I was able to login