Hi, : Defective fuel cap, cracked evap lines or (and) evap canister., evap sensor defective, fuel pressure valve clogged. Just to name few. If you have access to the Launch diagnostic, test the sensor live. It is a good thing to have the Factory service manual downloaded. Start the elimination process with the cap and the lines, then move to the electrical tests. Good luck! (It is also a good thing to stop fueling up the tank only to the first click)
Just want to correct my post: it is the Factory Maintenance Manual i was referring to.