the code for WeatherStationExtended comes with an own ThingSpeak-Library (thingspeakclient.h) from ThingPulse (it is part of WeatherStationColor-library, which confuses too). For some time, it is not possible to retrieve data from my "ThingSpeak-sensor". I tried to analyse the code but I didn't find the issue yet. Maybe the ThingSpeak-API changed in some detail.
I changed the code to use ThingSpeak's own library. Now it works fine.
Question: What was the reason to use an own library for ThingSpeak API-calls? I think this library needs an update to be used furthermore.