TLDR, the controller’s probably nonfunctional.
Quick, more in depth explanation:
Motor controllers use lil high power transistors called MOSFETs to modulate the power to the motors, and the part of the FET the control voltage to (which controls whether it’s conducting or blocking current) is called the gate. There’s a certain type of MOSFET that’s typically cheaper and better at carrying current (called an n-channel), but when used in certain applications like motor drivers, they need to be situated between the power source and the electrical load as opposed to between the electrical load and ground. Just due to some stuff with them conducting the high voltages (as opposed to the ground path), you need to use specialty chips to control the gate and thus the conduction, called gate drivers. If the MAX is reporting a gate driver fault, that likely means that one (or more) of the MOSFETs has blown or something like that - if it’s been given reverse polarity power or the outputs of two maxes plugged into eachother it’s very possible.