Assuming your sub is functioning properly, it sounds like your listening position may be in a bass null in your room, which would explain why you can’t hear changes in bass levels because the null will just cancel it out. I’d highly recommend doing the proven “crawl method” below to find the best spots in your room to place the sub for optimal bass performance at the listening position. Then once you find the right spot you can use the second link to easily and accurately set the crossover, volume, and phase on the sub (you really need someone help with adjusting the settings unless you can adjust them with software from your listening chair). Hope this helps, and best of luck
https://www.audioholics.com/home-theater-connection/crawling-for-bass-subwoofer-placement
https://lifehacker.com/how-to-properly-set-your-subwoofers-volume-without-sh-1506136549