Well, a solonoid is an electrically operated on/off or adjustable valve. This particular one is connected to the gas valve that enables the fuel to get to the burner. A driver is the thing that controls the solonoid valve. The logic circuit board's diagnostics think that the thing that opens and closes that valve (the solonoid) is broken (failed).
If it can't open the gas valve, it can't heat the water. Now, keep in mind that the diagnostics don't always point to the failure, but to a symptom. It could be the actual driver, or it could be the solonoid valve (maybe stuck), or the sensor that tells it where it is or even the circuit board itself.
At under a year, it should be under warranty, so first thing is to call them. Certainly, it can be fixed, but not all plumbers are really trained on the things or carry parts like they would with a conventional water heater. It's one thing to plumb it in, it's another to fix it.