Fuel flap won't open (Kamiq)

So I'm in a bit of a pickle. I'm about to go on vacation and the fuel filler flap on my Kamiq won't open. It's happened to me twice already, and both times I've been able to fix it by alternately pressing the lock/unlock buttons on my car keys while pushing in the fuel cap, but now it doesn't seem to be working.

I've been looking in the trunk for a button, lever, or cable I can use to unlock the flap, but there doesn't seem to be any, which is quite frustrating. Am I pretty much doomed to cancel my trip and take the car to the workshop, or is there something else I can try?