Tasmota flashed LED suddenly not longer working correctly?

Hello!

I have a TUYA LED which I flashed together with other LED to tasmota without any problems.
It worked for weeks without problems. Now I was away for three weeks and the LED is not reachable.
It connects itself to the Wifi which can be seen in the router, but there is no Web UI available and it is unavailable in Home Assistant.

Does someone know what the problem can be?
I tested the reset of the configuration with switching fast on/off seven times. But nothing changed.

Is there someone who knows how to fix such strange things?