This article explains what to do when a prompt appears to enable Accessibility Services when trying to launch an application

Some Android applications may require signature-level permissions to work properly.  For example, it is not uncommon for remote access solutions/apps to require signature-level permissions in order to launch without a user's explicit approval.  And when it comes to secured devices, like payment terminals, Android apps must be signed before they be installed on the secured device. 

As needed, Elo Touch can sign your application.  Please submit all requests to support@elotouch.com and make sure to include your unsigned APK.