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Usually when this happens it's due to a clogged or disconnected fuel tank vent. You need to check the hose or hoses the run between the tank and the filler opening to see if they are kinked or disconnected. Sometimes the vent hose runs inside the filler hose witch would require removal of the hose assembly to inspect it.(this may require removal of the fuel tank on some cars).
Also try looking into the filler opening with a flashlight and a long screwdriver to hold open the little flap at the opening ,see if there is any restriction inside the hose. It is possible the inside of the hose collapsed. The problem is almost certainly in the fill or vent hose between the tank and the fill opening.