Yes it is grounded correctly. The digital distro block is grounded to the frame and I have my two battery grounds (one to the trans and the other to the taillight ground, see pictures below). I have actually narrowed the problem down to my HIDs. When the headlights are off the digital distro block reads the correct voltage. However, when I turn the headlights on that is when the display will read 0.00 V. I originally had the HID harness +12 V attached to the under hood fuse box. I contacted Cullen at RSX Retrofits where I purchased my HIDs and he suggested running the + 12V from the digital distro block. As you can see from the pictures I have tried this as well and have ended up with the same results. To be honest I am out of ideas except to try another digital distribution block...
My digital distribution block is wired as follows.
Input: 2 AWG Power Wire
Output 1: Starter (250 amp ANL)
Output 2: HIDs (60 amp ANL) Has a 25 amp in-line fuse
Output 3: Under Hood Fuse Box (100 Amp ANL)
Circuit Breaker (100 Amp)