have a problem with my mamba max esc

[BrianG]

How is the BEC voltage at the receiver? And, might seem a stupid question, but is the throttle connector inserted the right way? If in wrong, you may get the RX to light up, but will probably be dim, and won't work right. It won't hurt anything though to try it the other way.

Do you have a spare radio system to try... maybe an old Traxxas TQ2/3? Just about everyone has one of those laying around. Being AM, I wouldn't run it unless you have to, but would isolate the problem.