My second floor hallway has a very bad squeak. I bought a repair kit called Squeak No More but its not working. I was able to locate the joists and I put a crap ton of their special screws in there but it did not help at all.

The floor is carpeted and I do not have access from below. I'm really losing my mind how to make this stop. Any thing else I can try?

Look at it as a last second early warning system. (assuming your bedroom is on the second floor)

Getting rid of squeaks in subfloors is not an easy task- and if screws didn't work - there is not a lot more you can do.

Remove carpet and padding then surface screw the entire hallway (into the joists) then reinstall carpet. If you aren't familiar with removing carpet best have an installer remove it carefully cutting the seams apart under doorways, you screw the floor while he goes outside and smokes a cigarette, then he can relay it.

If possible, live with the squeaks and fix them when you replace the carpet.

Consider yourself lucky we've got 'bouncy boards'.

When they installed the flooring in 1893, some of the boards didn't make it all of the way to a joist. They depended on the tongue-and-groove joints for support. Some of the tongues have since sheared away. Hence the bouncy boards as the GF calls them.

Yeah, if you've tried the screws, not a whole lot more you can do with a squeak. If it's more of a pop and not a squeak, sometimes those are wall issues and you can shim under the baseboard and under the wall plate to help take care of those.

We had a squeaker in the hallway, near the bathroom door. Lots of screws, new under layment, then some glue down vinyl planks. This is in our rental, so I think I'm done....nope, still squeaks. A search downstairs discovered a nail in the wall framing had worked loose and it and a couple others were driven back up into the wall. Nearly drove me nuts trying to locate that sucker.

I have one spot in a bedroom where the hvac ductwork is right against the floor. When you walk across it you hear bing bong!

gpbst3, you have a genuine Nightingale floor! You have just increased the value of your house-

Nightingale floors were floors designed to make a chirping sound when walked upon. These floors were used in the hallways of some temples and palaces, the most famous example being Nijo Castle, in Kyoto, Japan. Dry boards naturally creak under pressure, but these floors were designed so that the flooring nails rubbed against a jacket or clamp, causing chirping noises. The squeaking floors were used as a security device, assuring that none could sneak through the corridors undetected.

I saw where you could sprinkle talcum powder to stop board squeaks but that was on a noncaepeted floor.

Ugh. Looks like the only solution is to pull up the carpet.

Here's what I did on a previously house that had squeaky floors by the stairs... There was a kinda expensive carpet overlaid.
I call it the five dollar fix because the wood glue and the tool costs less than five bucks.

First, you take an ice pick and map out where the seams lie by gently pushing pick through the carpet and mark on top with any kind of tape for reference. (You just want to know seam runs and where to inject).

I had gone to the dollar store and bought a turkey broth injector syringe (which comes with an approximately 2" SS needle).

Second, get the container of white wood glue. A paper or plastic disposable small cup works fine.
Pour a paper cup of elmer's wood glue almost full and thin it slightly with water. Stir well. Fill the syringe with the thinned glue mix.

Then go down the marked seams and inject the solution into the seams at least a foot on each side of the squeaks. Make sure you stop injection pressure before pulling out the syringe needle. Refill syringe as necessary. You can disassemble the syringe and wash in water if desired to reuse.

Worked for me and didn't involve tearing up the carpet. It will dry and harden in 24 hours.