Dog is potty trained but when i look away, she isnt.

So I have a female yorkie who‘s very smart. I’m having an issue wherein she knows where the potty is and she knows to pee/poo there when I’m looking at her but the moment I do not supervise her (ie i just leave the door open to the potty area), she pees/poos on the floor. The potty itself is clean, I just washed it and all. I really don’t understand this behavior of hers. Does anyone have any idea why?

I even tried to heavily praise and reward her when she goes to the potty in the right place but still I get this peeing on the floor thing.