No changes , but no data

how to obtain what the problem is. For a long time working fine, now, for what reason ever, “no data”
What do I have to show here in the Community for getting proper advices ?

If you like, check out the website www reiair aqi eco (of course each gap to be filled with an dot)

https://aqi.eco/en/news

It looks like the sensor was “offline” for some time:
https://api-rrd.madavi.de:3000/grafana/d/GUaL5aZMz/pm-sensors?orgId=1&from=now-6h&to=now&timezone=browser&var-chipID=esp8266-5014169&var-type=BMP280&var-query0=sensors
But now the sensors seems to send data again since 9 hours.
Please be aware that we can’t speak for other sites than Sensor.Community and the grafana boards at api-rrd.madavi.de (where you can test a sensor before registering it).
So you should check our sites first if we receive data.