There can be a few reasons why the Primary Control Unit is not detecting the Secondary Unit.
First of all, we need to make sure when connecting a Secondary Control Unit, the device is turned off. We also need to check that the unit's battery is charged and that both control units have the same firmware version (Look here for how to upgrade the firmware version).
If you verified these but the secondary unit is not detected, please follow the steps:
Turn off the device.
Verify the communication cable connection between the Primary and Secondary Control Unit and tighten the Communication Cables nuts with pliers.
Turn back on the device. If it is still not detected-
Remove the communication cable from both control units, clean the connectors on both ends of the cable and reconnect it to the control units.
Turn on the device and verify that the secondary control unit LED is on.
If you still cannot recognize the secondary unit- replace the communication cable.
Please notice- you may need to rerun the FOTA process if the issue started after upgrading the device.
In case the issue persists, the connector is probably broken, and you need to contact your pHi-Tech regional representative to let him know of the problem.