Using an EHS36 with an EXP39 and T28P

I'm trying to use an EHS36 with a T28P and EXP39.

The T28P has firmware version 2.71.0.168 in it. We're using a 3CX IP PBX.

I tried updating the firmware in the EHS36 and the EXP39, but the instructions for setting this up are kind of old (back when 2.60.200.242 was current T28P firmware). So, I'm not sure that the firmware was actually updated in the EHS36 and the EXP39.

The physical setup that I'm using is:

The EXP39 "IN" connects to the T28P "EXT" jack with a short cable.
The EHS36 connects to the "OUT" jack on the EXP39 with a short cable.

Any suggestions on how to get this to work correctly?

John Rayfield, Jr.
Rayfield Communications
Springfield, MO