Problems with underfloor heating in a room

Has everything worked in the last few months? Unfortunately, I don’t see any flow indicator there. Are you talking about the room guest? Do all controllers respond to thermostat changes? Have you checked them individually? At night/in the morning when it’s cold and heating is on, you can check the flow/supply of the individual heating circuits at the distributor (by hand).

Did everything work in the last few months?
Unfortunately, I don't see any flow indicator there.
Are you talking about the guest room?
Do all controllers respond to thermostat changes? Have you checked them individually?
At night/morning when it's cold and heating is on, you can check the supply/return of the individual heating circuits at the manifold (by hand).

It seems it hasn't been working since the beginning of the winter period, but now I'm spending more time in that room.
Yes, exactly, the guest room is affected. Ok, then I will check the manifold for flow.

I would first test if all ERRs are controlling the correct heating circuits (we also had an error there). So best to set all ERRs to minimum once. After a few minutes, all "plugs" will then drop down (in your picture below, the gray parts that are red on the side). Then turn one thermostat fully up, wait a few minutes, and see if the correct plug moves up. Then do this one after the other for all ERRs. That way you would have ruled out this source of error.

You can see that the controller is closed on the heating circuit gas. According to Google, the Roth controllers are NC, which means closed without power, so the room is cold. Your WC/bathroom, for example, might also be quite cold. Turn the controller and observe if it moves, so that the cables are not swapped.

Huh? Bad and Gast are open after all.