Timing chain tensioner

I have a 2006 g35, I am going to install a new water pump, I know I have to depress the cylinder on the timing chain tensioner by pushing down on the little tab and simultaneously push the cylinder in but for the life of me I can’t seem to get it to push in. That cylinder pushes on a piece of hard plastic that is connected to the arm that pushes on the chain. I have already chipped a piece of that off. Is there something I’m missing in trying to pry that cylinder back.