My daughter has shown on & off interest in the potty too. She's 25 months old now, and still not potty trained! At first, she showed interest at home, and not at daycare. Now it seems like the opposite. She used to be interested in wearing "big girl panties" before, and now she chooses the diapers (pull-ups) instead. I think it's because of the characters on the diapers! But I discovered this weekend that if she thinks there are no more diapers, she will wear the panties. (We had run out of diapers in her cabinet in her bathroom, so she thought they were all gone). So I am going to try to hide them when we are home & make her wear panties more often. She does get upset when she wets the panties, but every time I ask her if she's got to go potty, she says no. I'm going to try to stick with her wearing panties most of the time to see if it finally clicks!
Oh, and when she does tell me she has to go potty, it's usually because she's already gone in her diaper, and she will go to the bathroom and change her own diaper HERSELF (I let her if it's not dirty), and refuses to sit on the potty.
One day they will get it.... one day...!!!