drives have small u before you push green button. then they should go to "1" with a decimal point to the right of it if the drive is ok.
If one of the drives does not have 1. then it is not ready and probably reporting to the control a fault. the control watches the drive fault contacts to be sure they are all ok; these are normally open contacts on C3 front screw terminal strip - pins 5&6. so you can check across these to see if you have 0 volts (good) or 24v (means it is open = bad).
the spindle drive and PA50 power supply also have fault contacts that need to be closed for the drives to stay on.
let us know how u do.