Have you tried charging the 12V battery with a standard 'smart' 12V battery charger? That might fix your problem. But you should check the battery voltage before charging. The Nissan LEAF had huge problems with its "keep the 12V battery properly charged" logic, killing quite a few 12V batteries, regularly. It would be interesting to monitor the voltage on your Bolt's 12V battery yourself. Do you have a voltmeter? (You should be able to easily find a rather inexpensive digital voltmeter.)
Since simply opening the driver door 'wakes up' the computer and other logic in the vehicle, thus increasing current draw on the 12V battery, the recommended testing methodology would be to pop the hood when you get home (so that you don't have to open the driver's door later to lift the hood and 'wake up' the car logic). Maybe even open/prop-up the hood (if the car is inside a private garage).
- pop hood when get home
- let car (battery) sit for an hour or so (making sure all the car logic turns off, and battery is at rest)
- test voltage on 12V battery, add data to your log sheet
- just before leaving in the morning, test battery voltage again, add data to log
- close hood, drive away (propping up the hood upon arrival, and then leaving it up, is a reminder to test voltage)
Sure, it would take an extra 60 seconds or so in the evening and morning to do this, but the results could be rather educational.
A 'fully charged' 12V battery should be about 12.6V. A 12V battery at 12.0V is seriously depleted (not empty, but far, FAR from full). (The best/only real way to test a battery is with a hydrometer, but voltage is 'good enough', unless you are going to write a scholarly dissertation on the subject.) If the Bolt's logic (and hardware) isn't keeping the battery above 12.4V in regular use, your battery will probably not last very long (a properly-sized 12V battery that doesn't have to crank an engine should easily last 8-10 years if kept properly charged). A 12V lead-acid battery that is routinely at or below 12.4V while being used (current draw, even low draw) will sulfate 'quickly' (in a couple of years or less) and needs to get a fully saturated charge every now and then to de-sulfate.
After a friend's 12V battery died in his LEAF (battery 2 years old), I bought a smart 'maintenance' (trickle) charger for my EV, which I use 2-3 times a month on my EV. It charges at less than 1 amp. I just attach it in the evening and leave it til the next morning, which fully, *fully* charges the 12V battery overnight. All that nasty crap sticking to the plates re-dissolves into the solution instead of continuing to build up on the plates and hardening.