Yeehlight LED lightstrip 1S going offline


I have some issues with my led lightstrips. They where working normally, but after a while it will go offline.

I can’t control it via all lights on/off. Also via google home I cant control them.
When i switch the power off and on from the strip it will connect again to my router.

All lights have a static IP.
Firmware version of the light is: 2.1.7_0018
Region is Germany

All other light from Yeehlight stay connected and are on the same way connected true my router.

Does anybody has an idea what to do?