Whirlpool gas dryer won't heat

Hello -

Need help. My Whirlpool gas dryer suddenly will not heat. I bought it used and do not have a manual with it. I’m fairly mechanical so if someone could get me headed in the right direction I would really appreciate it.

Everything else seems in working order. Timer, blower, ect. all seem to function properly. The heat issue just started all of the sudden.

Help!

Thanks.
Summy