Hi, I am Dave, I will help you with this.
Open the Settings App, then go to Personalization - Taskbar - Taskbar Behaviours
In there, you should find tis option - Select the far corner of the taskbar to show the desktop
Is that enabled, if not, re-enable that setting
If that was already enabled, disable that setting, restart (not shut down) your PC to apply that change, then re-enable that setting to reset the associated registry key.