Stepmom needs help!!!
My son really enjoyed reading books about children using the potty (though he's been ECed since he was tiny, so he was sort of used to the idea). We had a "potty pause" at around 19 months, and got over it by reading Once Upon a Potty and some Sesame Street book where Baby Grover "has to go." It just normalized it.
Latest favorite around here is Everybody Poops.
So, maybe you could try just reading those books to him for a couple weeks and then see if he wants to use the potty.
Oh, and also, my DS's latest thing is putting his lovey on the "potty"--we get a short fat cup--one of his stackers--and put the toy on it when we put him on the potty. He likes to tell us "Shelly go potty? Shelly go poop?" and that means that both he AND the doll need to use the facilities. Again, maybe play at putting a toy on the potty every now and then for a few weeks before you try to put HIM on it.