You have moved the truck lock into the locked position. Normally the trunk is closed, but not locked, so that it can be opened via the trunk release.
There are two reasons your keys are not opening the trunk. Either you are not turning the key all the way to the unlatched position (it should click twice), or you are using a valet key. A valet key will only work in the ignition and door latches, but not the trunk. Valet keys usually are missing the black rubber top, showing all metal.