Ya if your motors are beeping it just means there is no pwm going to them. Or the signal range could be out side what the ESC is looking for. So like most ESC operate on a pwm signal that should be between the ranges of 1000 to 2000 (1-2ms) So if you have a signal generator that say is generating a signal of 985 the ESC will beep like it has no signal, that might be what’s happening in this case. So that’s why all esc will have a throttle calibrate setting and the esc will recalibrate the min and max ranges to match the min and max to the incoming signal of the pwm generator (this case the hub).
Also the ESC looks at the signal when its turned on so if its out side the range when its turned on it will beep.
So what i would do first would be just to make sure its outputting a pwm signal at all. You dont need a oscilloscope or anything, you can just take a cheap multimeter and put the probes on the signal and ground line If there is no pwm signal i there would be like 1v or no voltage. If there is a signal it might be around 1.5v but if you go from min throttle to max you should see the voltage raise maybe from 1.5v to 2v. So with more throttle the voltage should go up. Im out of town so i can give you exact numbers but it should be close.