Solved! The Temperature appears only, if the printer is connected!
I've installed octopi on a new RasPi4.
Because i want to check, where the RasPi temperature goes to when using the live stream with higher resolutions, i installed the NavBar Temp Plugin, but it didn't work.
There are no temperatures visible in the Navbar (It's not the problem with the font color).
In init.py of the plugin, i already added the new BCM Type 2711 to the piSoctypes array but this also didn't change anything:
self.piSocTypes = (["BCM2708", "BCM2709",^M "BCM2835", "BCM2711"]) # Array of raspberry pi SoC's
Has anyone an idea?