Temp gauge not working?

I did add coolant last week to it. I also managed to get some pliers on the sensor cap so it is snug. The cap looks good and I took it for a little shorter drive today but let it idle for about ten minutes in the garage. The gauge stayed at the halfway mark and it never puked coolant.

Tonight I am running it out to a cruise in. It's in the next town over so I'll be cruising at 60 for a bit. Hopefully she says cool.