Pooing in the House
Dogs do everything in their lives by scent. In fact dogs do not use their eyes like humans, but that is a another subject.
If your dog can smell poo odor in the house that means this is the place to poo. Your email indicates he can smell poo on the carpet, although you cannot smell anything . But you are forgetting that a dog has a nose which is millions of times more active than yours. You have in the past cleaned to human standards not dog standards.
Dog standard cleaning goes like this.
1. Clean area with soapy warm water
2. 2. Then clean with plain cold wate.
3. When dry spray with a spirit, like meth’s, your pharmacy can advise.
4. Your dog cannot be allowed near the area till it is dry.
That should be the end of your problem