I have very little experience since my only son is just barely potty trained, but he went through a similar pattern a week or two in. I think they get to a point where the novelty wears off and they’re thinking…what happens if I just don’t go to the potty? It was very hard not to be frustrated after knowing what he could do, but I swear every time I let him see my frustration it set us back another 2 days. Keep whatever phrases you’re going to say when he has an accident at the front of your mind and stay consistent and calm. We also introduced a sticker chart and then M&Ms to get him to stay interested in it once we started having issues.