Basic Fixes:

• Restart the computer: A reboot forces all services and processes to shut down, fixing glitches and temporary bugs.
• Run a malware scan: Malware often triggers abnormal computer behavior, software, and hardware issues. You can use the built-in Windows Defender scan to remove the virus.
• Check for available updates: Update your operating system. Windows updates often come with bug fixes and, in most cases, will resolve minor Windows issues.
• Check for stuck volume key on your keyboard: If the slider key is stuck, the volume slider may not disappear from the screen, leading to the problem.
• Restart Windows Explorer: When you restart Windows Explorer, the computer resets explorer.exe, the process responsible for managing the user interface elements.

Fix 1: Disable and Re-enable Audio Device

An option to fix the non-disappearing volume slider is to disable and re-enable the audio device. This fix is very effective because it resets all related processes, including those connected to the volume slider. Follow the steps below.

Step 1: Right-click the Start menu and click Device Manager.

Step 2: Expand the Sound, video and game controllers category, right-click on your Audio Device, and click Disable device.

Step 2: Expand the Sound, video and game controller category, right-click on your Audio Device, click Uninstall device, and confirm your choice.

Step 3: Restart the computer, and the device should automatically be reinstalled. Once done, confirm that the fix was successful.