One other thought, sometimes you need to teach a dog to tell you they have to go. Some have been trained to avoid humans because they associate punishment with BMs and they tend to hide or avoid their humans when they have to go.
Overplay the "do you have to go" questioning and really praise the telling you as well as the actual going. Some dogs will really get animated when they have to go, others not so much.
I had a cliet that taught their dog to ring a bell when they had to go. That had it's down side, as you could imagine.