It sounds like your Windows 11 taskbar behavior has changed unexpectedly. Typically, when the taskbar is set to auto-hide, it should reappear when you hover over the bottom of the screen, even if a window is open. Since you now have to close your active window first, there may be a setting or an update that altered this behavior.
Here are a few things to check:
Restart Explorer: Open Task Manager (Ctrl + Shift + Esc), find "Windows Explorer," right-click it, and select "Restart." This refreshes the taskbar and may resolve the issue.
Check Taskbar Settings: Go to Settings > Personalization > Taskbar, ensure "Automatically hide the taskbar" is enabled.
Check Multi-Monitor Settings (if applicable): If you use multiple monitors, Windows may be handling the taskbar differently. Review settings under Settings > System > Display.
Look for Recent Updates: Sometimes Windows updates adjust system behavior. Check Settings > Windows Update for any recent updates that might have changed the taskbar behavior.
Try Different Window Types: See if certain apps prevent the taskbar from appearing—some fullscreen applications may override it.
Use Windows Troubleshooter: Run the troubleshooter via Settings > System > Troubleshoot > Other Troubleshooters > Windows Explorer.