Terry,
Can you please provide the firmware of the E27 as well as the version of the AE Touch Screen application. The E27 firmware can be located via the mobile app, navigate to the system settings page and click the blue i at the top of the page. You can find the application version of the AE Touch Screen on the about page. Once we confirm this information we can narrow down the issue.
To elaborate on Brads response, the system can disarmed with the Installer PIN, but only if it was armed with the Installer PIN. If the system was armed via the Master PIN or any other PIN, the error would result in a no authorization error as the Installer PIN is valid, but not authorized to disarm when armed by another user. This also includes single key arming.
Thanks – Mike