Trouble with PPS on u-blox 7

[gpsd]

Hello,

I'm having trouble getting PPS from a u-blox 7 device.

I've got a USB receiver that's based on the u-blox 7. A "ubxtool -p 
MON-VER" reports:

UBX-MON-VER:
  swVersion 1.00 (59842)
  hwVersion 00070000
  extension PROTVER 14.00
  extension GPS;SBAS;GLO;QZSS

When I run gpsmon, the value for PPS is simply N/A. I've also tried 
using ppscheck, which doesn't return any results. I do get a good sync 
to six satellites.

I get UBX-ACK-ACK when I try "ubxtool -e PPS" and/or "ubxtool -e TIM-TP" 
so it looks like the unit should support PPS. Additionally, I can see 
the device /dev/pps0 is created and lsmod shows both pps_ldisc and 
pps_core are loaded. It certainly appears that I should be getting PPS data.

I'm running Debian Buster with stock kernel 4.19.0-20-686-pae on x86 
hardware.

Does anyone have any thoughts/suggestions?

Thanks,
Roy