nap disappeared - 15 month old

[hazhawken]

hi there,
my 15 month old dd suddenly stopped napping two days this week - she usually has 2 hours in the middle of the day but for some unknown reason, she just hasn't gone down even though tired signs were there. This has happened the days we've been at home all morning, so maybe it's not enough activity !
Any one had similar or have any advice ?

My DS did this at a similar age for about 6t weeks. He is now 2.5 and would sleep for 3 hours in the day if I let him, but we keep it to 1.5 so he goes to bed before me in the evenings.