Hi Tom,
thank you for your swift reply!
This is very strange... I checked the string that is being sent every 5 minutes and it says "station=0". I took your advice and created station 1 and changed "station=1" in Weather display protocol. Now I have two stations but neither is receiving data?
This is the changed string: 
Station 0 Id = f075a04d
Station 1 Id = 1f075a04d
Hi,
suddenly Windy does not accept data sent from my station via Weather display anymore. Nor is the station visible on the map. It's been 19 hours now and the message is "Latest observation obsolete"
Sation Id: f075a04d
When I send data directly through a web browser, I always get this message - even if no data was sent for a longer period of time:
SUCCESS
NOTICE: Measurements not inserted to database because cooldown time 4 minutes (time since previous insertion is 0.00 minutes)!
Can you please check what is the problem?
Thank you!
Jure