Wait, no LEDs lit on the Jaguars? You need to check if you have connected power to the Jaguar correctly. Make sure not only the +12V and GND are connected to the correct side of the Jaguar (Red and Black screws) that marked V+ and V- (not M+ and M-). Also make sure you have the polarity connected correctly and there is a fuse for each Jaguar on the PDB. To be absolute sure, use a volt meter and check if each Jaguar has 12V across the V+ and V- terminals. If there is and the LED is still dark, your Jaguars may be bad.
Drive motors will be turned off after a tenth of a second by the Motor Safety feature if you don’t give them a command. You can disable the safeties for the duration of Autonomous (remember to turn them back on in Teleop), or you can continuously set their values in a loop.
BTW, I always thought motor safety is to safe guard buggy code from losing control of the robot. But then I think about it, even with motor safety, buggy code can still cause the robot to runaway uncontrollably. So the purpose of motor safety is really for safe guarding losing communication with the joystick such that the motors will stop instead of running at the last set speeds. Therefore, that’s why there is no point of turning safety on during Autonomous since there is no joystick involved. Is my assumption correct?
Your first thought is correct. The motor safety code is there to prevent a motor from continuing to run if the program doesn’t keep controlling it. There’s a separate system watchdog that shuts down all robot outputs if communication is lost.