You can clear out the Stores Temporary File Cache by running the below. This can help fix issues with stuck downloads in the Microsoft Store causing issues on launch.
1.) Press the Windows key + R shortcut to launch the Run dialog.
2.) Type wsreset.exe in the box and click OK or press Enter.
If that does not work you can re-register the Microsoft Store app using PowerShell.
1.) Launch an elevated (Run as Administrator) PowerShell session. (You can search for PowerShell in the Search bar and Right-Click to run as Administrator.)
2.) Copy and Paste the following command:
& {$manifest = (Get-AppxPackage Microsoft.WindowsStore).InstallLocation + '\AppxManifest.xml' ; Add-AppxPackage -DisableDevelopmentMode -Register $manifest}
3.) Press Enter
4.) Launch the Store app to confirm this resolved the issue.
Please let me know if this helped resolve your issue, if so don't forget to accept this answer.
Thank you and have a great day!