Removing Tow Hook Cover

I have a 2015 MCS F56. I want to buy a Platypus Pro License Plate Holder so I don't have to drill holes in my front bumper. The holder attaches to the tow hook on the left of the black bumper. It looks easy enough to attach, but I can't figure out how to remove the cover for the tow hook. The cover has a little arrow on the left side, but that doesn't seem to do anything. I trying to carefully pry it off, but it wouldn't budge. If anyone can give me a suggestion, I'd appreciate it. BTW, has anyone attached the Platypus Pro license plate holder to their Gen3 F56 or F55? Thanks