" Press Windows Key+X on your keyboard to display the Tools Menu and select Control Panel. Or, right-click the lower left corner of your monitor to display the Tools Menu and select Control Panel.
   Type UAC in the search field in the upper right corner of the window.
   Click Change User Account Control settings in the search results.
   Then do one of the following:
       To turn UAC off, drag the slider down to Never notify, and click OK.To turn UAC on, drag the slider up to the desired level of security, and click OK.
   You may be prompted to confirm your selection or enter an administrator password.
   Reboot your computer for the change to take effect. "

Try this; https://answers.microsoft.com/en-us/insider/forum/insider_wintp-insider_security/user-name-and-password-boxes-do-not-appear-when/9c541a4b-1311-422e-9a03-7438df093214 In terms of turning your UAC back, you can do the following: " Press Windows Key+X on your keyboard to display the Tools Menu and select Control Panel. Or, right-click the lower left corner of your monitor to display the Tools Menu and select Control Panel. Type UAC in the search field in the upper right corner of the window. Click Change User Account Control settings in the search results. Then do one of the following: To turn UAC off, drag the slider down to Never notify, and click OK.To turn UAC on, drag the slider up to the desired level of security, and click OK. You may be prompted to confirm your selection or enter an administrator password. Reboot your computer for the change to take effect. "