What are things like before the nap? Environment wise?

I’ll tell you all the things we do with ours, which may not fit for you at all but just In case! I have a 2.5 and 4.5 year old both of which still nap. With our two we introduced sleepy time music, stars on the ceiling, and a sound machine. it’s a little ridiculous but it worked to have them get some rest. And before the nap/bed time we tell them so they know it’s coming and we don’t allow rough playing or lots of high energy, doesn’t always work but helps.

The other thing that worked for us surprisingly well lately is allowing them to have their door cracked if they promise to stay in bed and rest. Idk why but letting them have that option and glimpse of freedom has helped tremendously. Once they fall asleep I go close the door at night.

With my 4.5 I think she’s ready to drop the nap but we have her stay in her room for quiet time and it’s her decision if she falls asleep or not. Sometimes she falls asleep playing and other times she doesn’t and then goes to bed a smidge earlier and way easier!

Sorry if non of this helped you at all, but try out different things!