How to tell if underfloor heating is running - ERR still without thermostat cover

Line A goes into the floor and Line B into the 100-liter tank? Both without intermediate display. Additionally, a picture of the distribution box below.

On the far left, the valve is open (at 100). You can also see this at the top of the blue part, which comes out of the actuator at the top. For now, you need to turn the ERR until the blue part in the actuator disappears. However, it may happen slightly offset. (1 minute) For the heating, wait for the instruction or take the manual. With the +/-7° you probably only adjust the heating curve up or down.

At 21°C the heating should actually be off, so no flow in the heating circuit either!

Screed program still active?

Only in one heating circuit?

Correct Normally everyone is then on. It had occurred to me because of the outside temperature.