You definitely need 5v connected then, USB requires 5v as well. Pin 4 of the multi out should be connected to 5v (check the main 4 layer trim guide for pin numbers), but you will also want to use your multimeter to ensure that pin 4 of each of the USB ports and one of the pins of the fan connector (probably the one with the red wire, red and black wires are almost always color coded with red being voltage source and black being ground/negative, although it isn't unheard of for someone to screw up and get them backwards) have continuity with it and are all getting voltage, they might not all be connected after your trim because the standard trim doesn't leave anything that requires 5v and just has you connect 5v directly to any of the parts that need it. It also wouldn't hurt to reflow your solder joints with some additional flux, I'm only getting a good view of the joints on your USB C board and one end of the wire connected to the USB ports, but the ones I can see look pretty sketchy. If you use adequate flux the solder joint should be quite smooth and rounded, if has an uneven surface with lots of spiky bits it isn't as strong and may make a poor electrical connection if any. Also it looks like you have stray strands sticking out from at least one of your solder joints, you really don't want those, they can very easily cause shorts. I would recommend desoldering all wires that have any stray strands (I can see them on your red wire on the USB C board, your other joints could easily have them) and cutting the end off all the way back to the insulation, stripping it again, then twisting the strands together between your fingers, adding flux to the exposed wire (I keep a tub of paste flux around just for this and dipping my solder wick in, I otherwise prefer a needle tip dropper bottle of liquid flux) and then tinning the wire with some solder before attempting to reconnect it. You are much less likely to get stray strands of wire sticking out if you twist and pre-tin your wires this way.