Will not take gas when hot and tank empty

I’ve been having some issues with my Impreza wagon lately. I appreciate all the responses to Fix a flat- 4 new tires.

Gas light came on yesterday but when I went to fill the tank… Gas would not go in and the tank acted as though it was full, spitting the gas back out.

I propped the valve open for 15-20 minutes and when tried to fill again, it allowed me to pump gas. Is this a serious issue that I need to address immediately? What if I never let tank go below 1/4 full?

I know that Subaru filler necks can have issues like this. There’s a breather tube that could be clogged. It basically expels the air as you fill up. If that air has no place to go, you won’t be able to fill it up.