Witt’s End

I’m new to this sub sorry if this is not allowed.
We have always had dogs and have never had an issue with them using the bathroom anywhere other than the backyard. We watched a friend’s dog and he refused to do his business anywhere other than our back porch. This has caused our dogs to start doing it too ( our porch is concrete). We clean it with the power washer every time they do it. We’ve used citrus scented soap, bleach, enzyme remover. We’ve also sprayed it ammonia and now vinegar after cleaning it but they still keep doing it. Does anyone have any suggestions on how to get them to stop?