Hard to start after putting gas in tank

When a car will not run right after refueling, it is usually the vent valve, that vents the tank.
If not opening, then using a small amount of gas will create a very strong vacuum, and not allow the car to run.
Try cracking the gas cap a little, to let air in and reduce the vacuum. Automotive Evaporative Emissions Part One

Possible causes - Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking The P0455 it's a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.

When is the code detected? EVAP control system has a very large leak such as fuel filler cap fell off, EVAP control system does not operate properly. Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors P0455 Buick Description This diagnosis detects leaks in the Evaporative Emission System (EVAP) purge line using engine intake manifold vacuum. If pressure does not increase, the Engine Control Module (ECM) will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve under the following vacuum test condition. The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this depressurization is implemented, the EVAP canister purge volume control solenoid valve will be closed.
if tightening the cap or replacing the cap does not help take your car to a shop to have it diagnosed as it requires special tools/equipment to test this and get an accurate results to find what needs replacing.

code p1456 refers to evaporative emission (EVAP) canister purge system(fuel tank system) -leak detected===causes--hose-fuel tank/pressure sensor--fuel filler cap--EVAP valve /bypass solenoid--EVAP two way valve---EVAP canister/vent valve

There is also a second reference to the code which is EVAP system leakage ====filler cap--EVAP canister purge valve--hoses---EVAP canister shut off valve---ECM programming---ECM

Check with the service dealer that the filler caps are interchangeable . It may be coincidence that the problem started after you changed caps or it may have shown a failure in the making

A loose gas cap or bad gas cap can cause this ,or filling gas tank while it running .or it could be a small leak in the evap system

Smells Like Change Symptom: Gas Fumes Change When: Driving Change Where: Passenger Compartment Change -->
Priority Action Part Type Cause 1 Inspect Fuel Line Assembly Loose or Damaged Fuel Line or Connector. 2 Inspect Fuel Filter Leaking Fuel Filter. 3 Inspect Fuel Tank PUNCTURED or Damaged Fuel Tank. 4 Inspect Canister Purge Valve Faulty Canister Purge Valve is Leaking. 5 Inspect Carburetor Dirty and Improperly FunctioningCarburetor. 6 Inspect Fuel Injector Dirty or Worn Fuel Injectors.

Common problem. Your engine is "flooding" (too much fuel). When the Evaporative Emissions Purge Control Valve (also known as purge control solenoid) sticks open, it allows the fuel vapor from the tank to be forced into the intake manifold on the engine when the vapor in the tank is displaced by the new fuel entering the fuel tank. This will cause the engine to start very hard (long crank) and when it does start, it will stumble and misfire for several seconds until the excessive fuel vapor has been cleared out.

If you scan your onboard Computer you will most likely get a code
P0441 "Evaporative Emission System Incorrect Purge Flow"

Your check engine light is most likely on. If it is not, it SHOULD be.

You may also get other codes such as P0455 "Evaporative Emission System Leak Detected (large leak)" or a P0457 "Evaporative Emission System Leak Detected (fuel cap loose/off)". If you do find these codes are present, I wouldn't worry too much about those because they can be caused by refueling your vehicle with the engine running. Simply clear all codes after replacing your purge control valve and everything should be OK.

Anyway, the purge control valve is located in the engine compartment and is not very hard to replace.

NOTE: DO NOT confuse the purge control valve with the canister vent control valve that is located at the REAR of the vehicle. I have seen many techs that do not know how these systems work that will replace the wrong valve and the customer is the one who ends up paying for it.

code p 0440 refers to the EVAP system --purge valve malfunction
check wiring and replace the purge valve

check fuel pressure relief valve