Refusing second nap only?!

Lauren • 💙 8/7/18 💙 3/2/21

My 10mo is has been refusing or having trouble falling asleep for his second nap for over a week now....anyone else having this issue? He still sleeps fine for his morning nap. About 1.5 hours. Everything I read says they don’t move to one nap until almost 14 months. How could he be showing signs already?!