GRP2612 with Poly Savi 8240 Headset - EHS cable?


I cannot seem to figure out how to get the Poly Savi 8240 headset to work with the Grandstream GRP2612 IP phone.

I have tried using both the APV-80 as well as the APV-63. Neither EHS adapter seems to work. The headset will not ring, answer, or hangup calls.

Is there any way to get this headset to work with the GRP2612?