when you put gas in it will not go in keeps turning off the pump on 2004 Chevrolet Silverado 1500

you can put gas in with a gas can it will go in but not at gas pump i put a new purge canister vale and still will not go in

2 answers
Any evap codes? Possible TSB issued to correct this, check with GM. Dealer.
is vent valve working or pressure sensor if equipped is your filler neck rotted. pump cannot breathe do you shut off car when filling up