Electric cart circuit, editied
In order to drive your 4 motors at their rated power you will need 4x14A=56A at 24V. I am not clear what rating your batteries are but I am assuming they are capable of 7A of continuous current (they will also be rated in Ampere Hours which will give you the capacity i.e. how long you can get out of them e.g. 70Ah would imply 10 hours at 7 amps if you could fully discharge the battery (which you cannot do without damaging it so the actual duration will be less).
If you connect your 2 batteries in series you'll have a 24V 7A capability. You are going to need a lot more batteries-16 in total. The reason the motors are not running is the batteries are completely overwhelmed by the load. You could try measuring the Voltage under load, I suspect it's way under 24V. Perhaps try making the measurements with 1, 2, 3 and then 4 batteries to see the effect.