Question

Why are suns rays never vertical on the Artic circle

Answer 1

sun rays fall on torrid zone because it is over head the sun but artic circle don't recieve maximum amount of sun rays because it is not over head the sun but far

Answer 2

As the earth revolves the position of the sun keep shifting between tropic of cancer and tropic of Capricorn. So the places located within this region gets vertical rays of the sun. however the area beyond this region does not get vertical rays of the sun.
I hope it's clear to you!