The underfloor heating is not turning on in one room

Thank you, then we will address that for the living room!

How many heating circuits in the living room? 1 or 2?

Or properly carry out the hydraulic balancing once...

Or do the hydraulic balancing correctly...

That would also be my approach now. Compare the set flow rates with those from the documents. Maybe only half the volume is set.

In the children's room, the underfloor heating does not turn on when we switch it on. However, it has already turned on by itself two or three times. Why, is beyond our knowledge.

In the bedroom, the heating is usually running at full power and only very rarely turns off – here too, we do not know why.

I have a question: how do you (or someone else) notice that an underfloor heating does not start or power up? Since it is quite sluggish, I wouldn't even notice this powering up or not starting... For us, for example, it is the case that the underfloor heating in one or two rooms is not active because the room already has the temperature, i.e., it is "heated along" by other rooms.

New FHZ must be run in. So open the heating manifolds. Set all thermostats to 30 degrees. Wait, now you have to observe that all heating circuit valves open. If they do, everything is fine. Now set the thermostats as they should be, no one seriously wants 30 degrees, and the valves close a bit again. If they do, everything is working. If one doesn't, call a technician. K.