HRV constantly low since one month Instinct 2s Surf

Probably just a seasonal change of HRV, which is common.

WeRo said:

I didn't wear them for about 3 months in the summer

That's another problem participating to it. The baseline adjusts automatically to the long-term changes in HRV, but you have to wear it in order to get the updates regularly. By not wearing it, the baseline remained on the level from the Summer, and now drops only very slowly to your current level (while your current level drops too, due to the coming Winter).

WeRo said:

What can I do?

You do not need to do anything. After a few more weeks, the baseline will drop sufficiently low to get you into the green. Well, you could reset the watch to the factory defaults - that would force the watch to reestablish the baseline from the scratch anew. However, it will take also couple of weeks, so you will not gain much time.

WeRo said:

I don't exercise too much

If you do not do any sports, you do not need to bother about this metrics much. It is important for athletes, allowing them to avoid overtraining, but for a common person, not doing any sports, it is not of much use.

Thanks a lot …then I will wait and see what happens.

I do sports every second day strength and running and between yoga and daily dog walks 

i check my last measurements before I stop wearing the watch and it seems you are absolutely right with the baseline 

That’s the baseline I had in June and July before I stopped wearing the watch