In your new screenshot you are still defining UC_COMPRD exactly on the same commodities as before, but now you try to define UC_FLO on RDEM* without any process mask. I cannot see how it could possibly work that way. I was suggesting completely different (UC_COMPRD for the demands, and keeping UC_FLO as it was).
I don't understand the logic in your model, but you do. Therefore, it should be easy for you to define the UC_COMPRD coefficients for the correct "Heat demand in the residential sector", and the UC_FLO coefficients on the "Heat supply by district heating".
As you could see from your earlier screenshot, you were defining the UC_COMPRD for the RESHXC101, RESHXC102, RESHXC103 commodities. If the sum of these commodities is not the "Heat demand in the residential sector", then the constraint is wrong, and you should correct it. Because I don't know which are the correct commodities that DO represent the "Heat demand in the residential sector", I cannot really tell you which they are. Only you know which they are, and so you just need to define the UC_COMPRD for them.
I don't understand the logic in your model, but you do. Therefore, it should be easy for you to define the UC_COMPRD coefficients for the correct "Heat demand in the residential sector", and the UC_FLO coefficients on the "Heat supply by district heating".
As you could see from your earlier screenshot, you were defining the UC_COMPRD for the RESHXC101, RESHXC102, RESHXC103 commodities. If the sum of these commodities is not the "Heat demand in the residential sector", then the constraint is wrong, and you should correct it. Because I don't know which are the correct commodities that DO represent the "Heat demand in the residential sector", I cannot really tell you which they are. Only you know which they are, and so you just need to define the UC_COMPRD for them.