Before doing below steps copy the below line by CTRL+C
%LocalAppData%\Packages\Microsoft.MicrosoftStickyNotes_8wekyb3d8bbwe
Windows Key+R > Paste by CTRL+V and Enter.
Now take the backup this entire folder
Windows Key+i > Apps > Click on Sticky notes > Advanced options > Repair.
If repair doesn't work, reset.
Uninstall and Reinstall Sticky Notes app (Data will not be impacted)
A. Uninstall - Right click on Windows Start > Click Windows Powershell (Admin) > Copy the below and paste into Powershell and Enter
Get-AppxPackage MMicrosoft.MicrosoftStickyNotes | Remove-AppxPackage
B. Reinstall
Right click on Windows Start > Click Windows Powershell (Admin) > Copy the below command and right click in Powershell to paste > Enter
Get-AppxPackage -allusers Microsoft.MicrosoftStickyNotes | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register “$($_.InstallLocation)\AppXManifest.xml”}
If above doesn't work - I would recommend that you perform a Windows 10 repair upgrade. Repair upgrade fixes all Windows errors and retains all files, applications and settings. (You will not lose any data while backup is a good idea) Below is a good guide to perform repair upgrade
https://www.tenforums.com/tutorials/16397-repai...
Disclaimer - This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.