Windows 10: Taskbar Won't Auto-Hide in Full-Screen Video/Game Mode

When watching videos or playing games in full-screen mode, the taskbar remains visible at the bottom of the screen and won't auto-hide. I've tried various solutions, but the problem persists. I want the taskbar to stay visible when using the app in windowed mode or during regular use, but I want it to auto-hide when I switch to full-screen mode. Please help.