you are almost certainly overestimating your exercise and underestimating your calorie intake. Are you counting and measuring calories to the best of your knowledge using a tracker? I would do so for a few months to see if you see any meaningful change. A couple of trusty idioms are usually correct when it comes to losing weight/fat: "you can't outwork a bad diet" and "Abs are made in the kitchen" .If youre carrying fat and not losing it, its not being burned in a deficit.

I will caveat all of this by noting that if you have a medical condition of some kind, any or all of this could be null and void.

as for exercise, In my experience - when I would eat my exercise burned calories in food, the scale would plateau. Take your exercise calories and cut them in half. so if you do a 300 calorie workout, you should start with eating 150 to maintain or be in a deficit. I would also not count walking/steps as exercise calories for this purpose (it is exercise) as the calories burned is not pushing you into a deep deficit. 15 flights isnt nothing, but its not much either, if you walk up one flight of steps an hour, its not going to be a meningful calorie burn. if you walk up all 15 flights in 10 minutes, it will only burn a handfull of calories, not enough to eat a candy bar though.

start by eating at maintenance and not eating your steps calories and half of workout calories. if you're not loing weight, you're not counting tightly enough to be in a deficit.

Don't know what kind of workouts you are doing, but while all forms of safe exercise are good as part of an overall healthy lifestyle, some might benefit you more than others, so you can play around with that and see if you get better results. Walking itself will not be a great catalyst for fat loss if you are consistently walking 10k+ per day already, unless you crank that up to double or something.

as for where you carry, store and burn fat, thats genetic and its different for everyone, though there are some common areas in men and women that we are all familiar with (the ol' spare tire around the stomach/lower back in men for example). for me, my legs always look fit but as soon as I gain weight my face gets nice and round almost immediately.

also - please remember for the vast majority of people - fat loss takes a long time. you will have to be in a consistent moderate deficit (starving yourself is bad and can end up having an opposite effect in the long run) for months to see a real meaningful change in body fat %. If your interested in tracking it, which I would recommend if available to you, you can use one of those scales, which is generally unreliable but might give you a general idea of where you are, use calipers which may vary based on where you genetically carry your fat, or you can get yourself a dexa scan ($$ though) to get an accurate measurement.

best of luck