Room with underfloor heating ice cold

hello, house completed in 2015. We have underfloor heating. I just got a shock when I opened the playroom. It was ice cold, including the floor in that room. All the others are warm... I opened the distribution box. There are these little tubes for each room like the ones used to measure the water level in plants. For this room, the tube is at the very top... could it be because of that, can I do something myself or should I call the plumber? I have turned up the regulator in the room for now...

Actuator could be broken, we have had that before as well.

I have now looked. They are the tascosetters. For the mentioned room, it is set to over 2 liters up to the full stop. Could it have something to do with that? And can I adjust something here myself??

The tubes probably indicate the amount of water, which is needed for the hydraulic balancing.

Hello, I have now set the room to maximum. Now it is getting warm. hm