I'm using a Bostitch MIIIFS that I've rented from Home Depot to install Brazilian Cherry and the staples just don't seem to get recessed enough for the next row to fit over the tongue without manually punching down the staples.

I've tried adjusting the PSI of the air compressor up to 125 PSI and that still doesn't seem to do the trick. Any suggestions would be appreciated.

At over 100 PSI, a properly operating M111 FS will blast the smitherines out of that tongue. Either the tool is malfunctioning or the compressor doesn't have enough power and it really ins't that 125 PSI you stated. Take the tool back to HD and take a board with you. Have them use a compressor there and determine if it's the tool, the wood or the compressor.

It may just be the brazzilian cherry. If some of the staples are setting and others are not this could be the case.

Thanks for your help guys. It was a bad stapler. I took it back and received another MIII and it workes great at 85 PSI.

Glad the problem is fixed. If it happens again, I have just cut the staples with a pair of dikes and hammer/punch sideways into the tongue. That way it holds down and back just like a L nail from the floor nailer. Better than trying to pry them out (impossible w/o tearing up the tongue).