On a computer running OS X El Capitan (10.11), a USB-eLicenser is not being recognized by the eLicenser Control Center. Licensed applications cannot be started. The following error messages may appear:
The problem might be related to Duet, an app allowing you to use an iPad as a second monitor. It should not occur when the latest software versions are installed.
Therefore, please update Duet, the eLicenser Control Center as well as OS X El Capitan.
If the issue persists, we can only advise to quit Duet before running your eLicencer-based software.