Temperature reading failed (Newbieproblem)

Hello friends,
I am from Germany to Lower Saxony and am 33 years old.
I have buy second hand my Finder at 3 days and I love the results.
The Finder is a used printer with 37 hours.
Now I have an error message after 3 prints and I am a absolute beginner.

When i start the printer and heating a printer, this heats up 300 - 400?.
When i restart the printer, comes a Errormassage "temperature reading faild, please check the connection".
Can anyone tell me what you have to do here?

Attachment 12390

Greetings from Lower Saxony

Tobias