Why can't I fill my car with a gas can?
”The most common reason why your fuel tank is not filling up is because you have a clogged or a faulty evaporative emissions control system (EVAP). ... If your EVAP is clogged or faulty, you won't be able to fill your gas tank.”
How do you unclog a gas tank vent?
Disconnect the canister vent line to the gas tank, and try blowing through it. This is a short line, so it should be obvious if there is a blockage. If it seems it might be clogged, use compressed air to thoroughly blow out the line.