My new(ish) ipod nano will not rotate from portrait to landscape.

My newish ipod nano won't rotate from portrait to landscape. It used to do it fine, but recently this has just stopped working. I have looked at people's conversations talking aboout the rotate lock button; can't find it on this ipod nano!! But if I don't know where it is, I don't see how I could have recently turned it on either? Does anyone have any suggestions on where this button might be, or how I can get my ipod to start rotating again? Thank you 🙂