Sub floor I meant. Also depends if you used the firm you bought the floor from to fit it then you have far more reason for complaint. If they were separate then makes life a lot harder.
I lifted the floor in one room and put green boards down, it was ok for a week then slowly gets worse and after a month just as bad. I am now going to bin the lot and start again with stick down LVT. There should be no issues at all with that. Frustrating as I am paying twice but risk of paying...
I have this same problem, we had 90m2 laid in March and the cracking is so bad. I have had two people out and they can only suggest the green boards underlay rather than the grey XPS so worth a go in one room initially. How did you solve it and what was the cause? It is driving me mad as I hate...