Something might have changed. Just check what is your default E-mail application and do reconfigure it or run a repair command (for Outlook for example). Reboot to make sure that the changes are applied.and, if need be, reinstall the Control Center again.
Open the scan to E-mail configuration and select the application that handles the E-mails.
If that does not work there is a workaround: Scan to pdf then send the pdf file as attachment. From your E-mail account you may also be able to insert a file acquired from the scanner.