I am trying to replace a cracked screen on my 2017 iMac 21.5" 4K. The cracked screen worked perfectly—minus the crack....

Same issue here. I upgraded my 2017 21.5 iMac to 32 GB RAM. Everything fit back into place and works like a charm… except the USB-C ports. I’ve tried all the USB-C cables and adapters I can find. No luck. Do people think this is a problem with the RAM, or is it more likely that I somehow damaged the USB-C ports? Update (01/15/2019): I ended up solving the issue. I think there was probably a slight misalignment between the port and the case. When I looked at my computer I saw that it looked a little off. So I stuck a USB-C in and just put pressure on it toward the direction I thought it needed to go. After a few seconds of pressure, I heard a “snap” and then the port started working. I was definitely worried about breaking it, but I figured I had nothing to lose so I just went for it.