This app can't be activated by the built-in administrator
Press Windows key + R to open up a Run dialog box. Then, type “gpedit.msc” and press Enter to open up the Group Policy Editor.
Inside the Local Group Policy Editor window, use the left-hand pane to navigate to Windows Settings > Security Settings > Local Policy > Security Options.
With the Security Options policy folder selected from the left pane, move over to the right pane and double-click on User Account Control : Admin Approval Mode for the Built-in Administrator Account.
In the setting window of the policy, you’ve just opened, expand the Local Security Setting and set the policy to Enabled. Then, hit Apply to save the changes.
Close the Local Group Policy Editor and restart your machine. At the next startup, you will be able to use Windows Apps from the built-in Administrator account (the ones that won’t require your Microsoft account).