A picture of the vent would help. There are a couple methods used to retain the vent flap. I believe to open the vent you have you push up on the "clips" with your thumbs and rotate them out. My vent has 2 small clips that you just rotate out of the way of the vent which would be different from yours.
2014 Palomino Puma 25RS
2011 F-150 Super Crew XLT
Days camped in 2014 - 23 Camped 2015 - 47
Camped 2016 - 58 done - 13 more planned so far
2017 - 14 nights reserved