N.S.
Both my daughters did the same thing. They were both interested in using the toilet, then they lost it. I let it be and they just started going again. Both times however, there were minor changes going on in the home. With the older one, I became pregnant during the begining of her training. So I put it on hold and about a couple of months after I had the baby she saw intrest again. For her is was a little slow. She peed in the toilet, but wanted a diaper just to poop and then back to the underwear. It was a bit frustrating buying diapers just to poop. One day i told her that I was out of diapers and sisters were too small. So she went in the toilet and was so proud.
My youngest, her issue was that it was near the holidays and I had read not to potty train during those days. So I stopped. The holidays past and she got her toddler bed and within a week or two, she was full on potty trained. So check if there are any changes in the home. Even the smallest change can effect them. Then wait 'til things settle in for her. If she is telling, even though it's too late, she is still interested, she knows what is going on. My youngest did not like the traininig toilet. i bought her the small seat that sits on top of your toilet seat, they have fun designs.