You have VBUS on the schematic, are you powering it from a PC or laptop USB port? Lots of USB ports are current limited to 100mA and your schematic has two RF amplifiers on it that can each draw 100mA typical and can reach peaks of 300 mA according to the datasheet. That's for each one. So you should have at least 1A @ 5V available, and should try it from a USB charger or a bench power supply to rule out USB current limiting.
Also, even if it's not a USB 100mA current limit issue, some PC USB ports are just bad at getting the 5V right, and are often on the low side, so check that too.
As for 12V being 4.72V , it's clear to me that your sc4503 switcher is not switching. Vin @ 4.72 volts is just passing straight through the inductor and diode to the 12V rail, so check your switcher, maybe it's blown (triple check your soldering there too ... )