get enough leverage on the piston cylinder. I guess I really didn't apply enough. I'll also try out Chris's recommendation to place a dime in the tensioner gap. Then, I'll snug it up with the pry bar.
Correct me if I'm wrong but I believe all that matters is the tensioner gap sits between 3.5mm and 5mm and that all the belt marks line up to the gears in the end.
I'll measure the belt deflection just in case this auto tensioner is "over-tensioning".