Station doesn't connect to netatmo servers anymore

[aeppler42]

I had my outdoor module at Netatmo in France for repair because of quick battery drainage. The system continued to work with the rain and wind sensors. After I got the outdoor moduke back last week I successfully connected it again to the station and it worked for about two hours. Then suddenly I saw, that the station didn't synchronize any data anymore, neither it's own indoor data nor outdoor, wind or rain. I can still access my account on the netatmo servers from the android app and the only info I get is the very last measurement from last week.
My internet is up and working and I have reconfigured the station connection to my router without getting any error message. The app congratulates me for a successful connection!
The only strange thing is, that my Netgear R7000 router doesn't show the station mac as connected device.
Any idea what caused or how to fix the problem? Currently my 300.-€ netatmo equipment which I got 3 month ago is a piece of junk and if not fixed soon has to be returned to Amazon.