Line under app icon in taskbar after app is closed

1. Restart Explorer: Press Ctrl + Shift + Esc to open Task Manager.
Find “Windows Explorer”, right-click on it and select “Restart”. 
2. Check for Windows updates: Open “Settings” > “Update and Security” > “Windows Update”.
Click “Check for Updates” to install all available updates. 
3. Reset Taskbar Settings: Open Settings > Personalization > Taskbar.
Turn off the “Lock Taskbar” option and then re-enable it.
4. To reset the taskbar using PowerShell: Open PowerShell (with administrator privileges).
Run the following command:
powershell
Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register “$($_.InstallLocation)\AppXManifest.xml”}
5. Contact Microsoft Support: If none of the above methods work, it is recommended to contact the Microsoft Support team with detailed error messages and screenshots for further assistance.