Need to know a few things:
1) Full Windows version number xxxxx.xxxx format (please use winver.exe to check).
2) Full Start11 version number
3) Is your start button on the left or centered?
4) Is the Enhanced taskbar enabled?
5) Is your taskbar at the bottom, top left or right?
6) Are you running multiple monitors?
Also, do know that you can only use a custom Start button if aligned left without enabling the Enhanced taskbar.