Zum Radio MMDVM-Pi DMR - audio issue

[KJ7DX]

Need some help...I am setting up a Zum Radio MMDVM-Pi board as a simplex hotspot. This is the one that has no onboard RF, but rather, connects to a radio. Using a Motorola CDM1250. I am not getting any audio out. When the MMDVM board keys the CDM1250, I am seeing the green activity light on my DMR HT, but no audio. I have tried the following:

*Tested DMR HT on a busy TG via a local DMR repeater and I can receive audio OK there
*Tried mmdvmcal by SSHing into pi-star. Turned on the command for the DMR test tone, adjusted TX offset and TX level as far as possible up and down, and no tone coming through the DMR HT.
*An analog radio on the same frequency hears the "digital noise" when the MMDVM radio transmits, and also hears the CW ID ok
*DMR parrot (9990) is responsive; comes back with a duration equal to what I sent out, but again, no audio, just a light on the DMR HT indicating activity.
*Pi-Star shows gateway activity on the hotspot, in and out, with low BER (0.0-0.1% usually, saw 0.3% once)

Other observations:
*RX Clip LED never goes off, no matter how much I adjust the RX level pot on the MMDVM board. The instructions say to adjust the RX level until the RX Clip LED barely turns on with no audio input, but it doesn't change at all
*DMR LED on the MMDVM board never comes on, whether I am TXing or RXing through the hotspot

I have set up the CDM1250 for flat TX and RX audio, so that should be correct.

Hoping that someone might have a suggestion on how to proceed. Thanks!