Corsa 1.2 twin

could be plastic strap is jamming inside it
make sure car unlocked when trying to open fuel flap
Gently try to open flap push on it a few times
May be able to pry open gently with car key if it is the plastic strap that holds the cap to the flap causing the problem

i think you should do minor engine service

If I remember rightly you turn the door key once
this unlocks the driver door
Turn a little further to unlock the passenger door and fuel cap
On the Zafira you could then remove the key and press the "open"
logo.
Failing this I suggest you open Youtube and search for Corsa fuel cap.
Always a good source for this type of problem

Hi Preven, The links below are YouTube videos showing how to clean fuel injectors, Also there's videos down the right side of the links that may help as well....................CHEERS..
Fuel injector cleaning without expensive tools

Improvised fuel injector cleaning with battery and bullet

I'd try to have someone help push the fuel flap, (cover) and you try to carefully pry open the cover. It may require multiple hard push on the button. Issue could be lubrication bent, misaligned catch, electrical button, or wiring connections. Possible vandalism. If you get it open, leave it open until you can get it fixed. Warranty? Google your problem, you may find others have same problem and have a "fix" for it.

The petrol flap doesn't have a lever to open it like other cars but can be opened when the car is unlocked by pushing on one side of the flap to open, if this will not open then the fuel flap locking actuator is faulty and has not unlocked the fuel flap, if this has occurred open the boot and on the left hand side of the boot you will see a round button, if you cannot see this and you only see a hole then chances are the side cover has been off at some stage and the button hasn't been reinstated, if it is there, pull on it and it will pull the fuel flap locking actuator back allowing you to open the fuel flap.

https://www.newbeetle.org/forums/questions-issues-concerns-problems-new-beetle/27899-fuel-door-wont-open.html

Remove fuel tank filler cap.

Push back release rod - 9 - by operating remote control unlock and remove bolt - 2 -.

Remove rubber part - 8 - from tank filler flange and swivel out tank flap unit - 1 - from side panel - 7 -.Assembly piece - 4 - and actuator - 6 - is installed.

• Install tank flap unit - 1 - (rubber part rolled up) with hinge side first.
• Bolt tank flap unit - 1 - and assembly piece - 4 - with bolt - 2 -.

Tightening torques: Bolts - 2 - 1.5 Nm

• Remove side luggage compartment trim.
• Disconnect harness connector at actuator - 6 -.
• Remove actuator - 6 - using special tool Socket wrench T 10010 from angled mounting bracket.
• Remove actuator - 6 - together with release rod - 9 - from seal - 5 - and assembly piece - 4 -.

Installing
Installation is reverse of removal.
Tightening torques: Bolts for actuator - 6 - 1.5 Nm .

Trace the fuel line. It will either go to the pump at the block or straight to the pump in the tank. Good luck

There should be a cable you can pull, around the area of the fuel flap. Open your hatch and check under any carpeting or interior coverings/compartments for something to pull.