Is it one particular bathroom that is the issue or is it that he does not wish to enter ANY bathroom? If you only have the one bathroom then this is a mute point.

My youngest son potty trained early - a little over 2 years old. We were so thrilled. And then, for no known reason, he refused to use the toliet and we were back to diapers. He eventually potty trained by about 3 years old. I still do not know what in the world caused him to regress.

My oldest son did not potty train until he was almost 3 1/2 years old - and then one day he just announced that he was wearing big boy underwear to daycare and that was that. I have no idea what caused him to decide.

So I would have to agree with what others have stated that the best approach is to be supportive and provide the facilities - making sure there is either a potty chair or an insert so they don't fear falling in, a step stool for putting their feet on once they are on the adult toliet, easy reach for toliet paper, etc. The rest is really up to the child. If you push it - it is likely to turn into a power struggle.

Perhaps you can arrange a play date with another child who is already potty trained. Perhaps some peer interaction will help. ?? It really is up to the child.

Hang in there.