Keep getting P0440 code on 2001 Chevrolet Blazer

I got 440 code, had a smoke test done, repalced vapor lines. light came back on 3 days later with same p0440 code. had vent valve replaced. light came back on 2 days later. same code again... please help

Surely the gas cap has been replaced with one from GM. SURELY. Have seen aftermarket caps fail right out of the box!
So your thinking its just the gas cap? Even though I have already had 2 smoke test done? That would b great, considering I have already spent $350 in repairs in 2 weeks all for the light to come bck on. :(
Fixed several with just a simpe fractory gas cap replacement! Fixed one for a customer that had spent 500.+/ with a gas cap!! This is just a guess but one to consider. This was an Impala 2002. Smoke test can be very effective IF at that time failure is present!!
I will try that thank u, wish me luck ;-)
You got it!