keep getting check gas cap on my 2007 buick allure already bought new cap and its still happening any suggestions pls

Could be a bad vent solenoid.

vent solenoid is the most likely, but it could be half a dozen other things in the evap system or a leak in the filler tube/tank/vacuum lines etc. do you have any codes?

Try lightly sanding the filler neck (put a rag in the opening to catch any crap) where it seals to the gas cap, and apply a thin coat of grease to see if it seals the cap. Probably something of a more significant nature, but always good to check the easy stuff first.

chances are its (like justin said) something in the evap system. this wont hurt the car but you will fail emissions unless its fixed.

I have had Evasp codes from poor sealing caps before. Generally speaking the first thing I do is go to dealer and get another cap and try it first. The rubber seals do not last forever.
Here with air-care (emission testing stations) they also have a machine that pressure tests the cap. Not uncommon to have them fail. Try a new cap!