Bostitch hardwood flooring stapler. The Staples misfire. I have to keep pushing on the Staples to make the gun fire properly

Have you been oiling it regularly? Compressed air is very moist so a few drops oil oil in the unit is needed every once in a while to lubricate it properly, try and see what happens.

Put a little gun oil on the staples the spring that helps feed them might be catching

Sometimes a gun will double fire, quickly fires twice and is caused by worn trigger valve or safety foot. However, two staples driven with one shot indicates that the staples could be the wrong gauge for the gun or the driver is damaged. The driver of a nailer has a taper on one side of the blade to prevent the driver from hitting two staples. The taper will push the remaining staples back into the rails. Make sure that the taper is facing the staples and that the staples are correct for the gun.

Ive had the same problem where it was putting divits you could see from the staples, we ended up changing out the flooring completely. Only thing besides trying diff psi's to get it perfect and different length staples/different heads on staples(nails) , maybe try staple gun. Keep trying every woods different, odd that it started half way through job.. odd.

You shouldn't have to do anything to the MIIIFS flooring stapler to shoot 2" staples. It is designed to shoot 1 1/2" to 2" staples right out of the box. If your stapler won't feed 2" staples, check the magazine all the way up to the power head for any foreign material that may hold up your staples.

If you have a Bostitch MIII FN it is only for cleats. Bostitch doesn't make a universal nailer that takes staples and cleats. The MIIIFN is the "floor nailer" and the Model MIIIFS is the "floor stapler"
Maybe check exactly what model you have and ensure you are not trying to put cleats into a stapler.

are the nails proper for nailer? the gauge of the nail is important

There is a spring to push the staples into place. Bostitch was purchased by Dewalt and moved their parts lists to the web address below. Enter your model number and order the parts needed. Good luck with your future projects.
http://servicenet.bostitch.com/

You could try finding your stapler and repair solutions oneReplacementParts.com They have parts, and guides to help repair this stuff.

!) Staples are jammed...clear out.
2) No staples... fill with staples
3) push down on handle to fire staple