P.M.
This is so normal – the thrill is gone, and pottying is just another obligation.
With my grandson, we bridged this transitional stage by turning pottying into a game, or going and sitting near him and reading favorite books. To lure him to the potty, whenever I noticed he was doing the potty dance, I'd go into the bathroom and begin to noisily wrestle all those dinosaurs out so he could find room to sit on the toilet. Especially the baby dinos, which were always covering the seat. Grandboy could not resist that game.
A little creative drama can help the child maintain her sense of play and humor, and this helps with all sorts of mundane activities and chores. My grandson is 5, and has long since gotten past his resistance to taking time out of his play. But that did last a few months. Remember that these are still very young children, and they need plenty of positive appreciation for their accomplishments. Trouble starts when we begin to take them for granted.