Let this be my mistake and not yours.... triple check EVERYTHING that you touch when dissembling something.
Problem was with the ribbon connection on the back of the gauge cluster. One of the connection points (where the harness plugs into the gauge) had gotten folded over and tucked under itself upon removal somehow. But, it wasn't noticeable when I removed the cluster the first time to check the actual connection strength at each plug. All in all very simple but frustrating fix. Hope this just helps people to remember to check your work and then check it again, and then because we own Z's check it again!