Four switch buck boost converter with UCC21520

Hi guys,
I designed a four switch buck boost converter with two UCC21520 gate driver ICs. When I supply the VCCI & VDDA of 5V and 12V to the gate drivers, there's a voltage output of around 2V in the output terminals. When an input voltage supply of 15V is connected, and PWM signals are provided using a F28379D launchpad (open loop), I receive around 8V in the output without connecting the load. When I connect the load there are pulses of output voltage. I don't get the desired output voltage. What have I done wrong? How do I correct this? I have attached a schematic of my design and a capture of the output waveform as well.

Thanks