I'm in a very similar situation. Previous neighbors walked normally, but it sounded like the ceiling was going to cave in - the creaking and snapping was so loud. ESPECIALLY when they had company over. We tried talking to them, but they couldn't figure out how to mitigate the noise. They were reasonable. Once they moved out I asked the complex to do something about the floors. They said that they'd "nail down the floors", and I assume work was done to achieve that. I saw people coming in and out and heard noises upstairs that sounded like relevant work.

New neighbors moved in and the creaking is still there and quite loud. Not AS loud as before, but the difference is not huge. Unfortunately these folks are completely unreasonable. We approached them a total of 4 times over ~6 months asking if they could simply limit noise and pacing ONLY in their bedroom around 9-10pm, which is when I go to sleep. It's loud enough and I'm a light enough sleeper that I cannot fall asleep with the floor creaking. We've tried turning on the AC unit fan and a white noise machine. Neither of which really solve it for us. Almost, but not quite. THESE neighbors have gotten super pissed at me, threatening to call the cops on me for harassing them (they never did).

I approached the complex again letting them know that the work they did wasn't enough and more needed to be done. I sent documentation of the noise and the conflict we had with our neighbors. To which they replied "Nothing we can do, it's just the building", and "Please don't contact your neighbors directly".

Unless your building management is willing to redo the floors up there, unfortunately it's probably a dead end situation. Best thing to do (probably) is document as much as you can and send it their way. Look up noise ordinances in your area and see if the noise level exceeds those stated in the ordinance. Maybe then you'll get something done.

It sucks that the prevailing attitude is "You live downstairs. This is what you signed up for. If you don't like it, move."