Your schematic appears to be twin interleaved, buck type, synchronous operated.
Try starting out with a single basic buck converter. Use just one mosfet and one diode (asynchronous operation). See if your control IC operates properly. If it does, then add another section of your design.
At 200 kHz your smoothing capacitor can be 1 uF. (It reaches output voltage fast as compared to your values totaling 2,000 uF).
If you get no output, then try driving the mosfet manually from a pulse generator. Gate voltage needs to reach more than 12V, so that it can turn on an N-device at the high side (N-device placed close to positive rail).