PSA to DIY battery installers

In my 2014 Volt, I recently had my entire instrument panel go blank and refuse to turn on. That sure was fun, not having a speedometer (aside from Google Maps on a phone mount) and not having any idea how much range I had left on gas or battery. The heater (when running on battery only) and the audible clicking noise for the turn signals also stopped working at the same time.

I searched online and found a couple forum posts about checking fuses and also disconnecting and reconnecting the 12V battery in case there was a loose connection. I had no luck with the fuses, but the 12V reconnection worked!

The connection didn't actually seem loose when I started. ~~However, when I replaced the 12V myself a few months ago, I had some terminal protection spray left over from a battery change on a different vehicle. I decided at the time, "hey why not use it here too? My Volt battery needs to last longer than that other car's anyway." Big mistake, I suspect this may have been the issue. I noticed once I disconnected the negative terminal that a bunch of the terminal protection stuff somehow migrated to between the connector and the battery post (only on the negative side). Maybe it really *was* just loose, but also maybe don't bother with the spray. It's all inside the car anyway, not exposed to the elements.~~

Anyway, cleaning all the stuff off and then reconnecting the 12V fixed all the issues I was seeing. It was a big relief, there are some scary high prices people were listing on those forums for replacing the display entirely if that was the issue.

*Edit: from the comments, it seems the spray was probably not the issue, but disconnecting and re-connecting causes a "hard reboot" of the system. This may indicate more problems coming down the line. But I guess "reconnect battery" as an easy fix is the takeaway here.*