Our floor used to squeak very badly in several spots. Fixing a squeaky floor can be a challenge.
Floors squeak for a variety of reasons. The most common is the nails that hold the sub-floor down coming loose from the joist and squeaking.
Fixing them means getting under the house, unless we're talking about a floor that isn't a ground floor, or getting under the house isn't an option. If that's the case, good luck.
The kit that's sold in stores that uses break away screws through the carpet did not work for me. It made the problem worse in our situation.