Fallout – Can’t repair molecular relay

You need to be allied with a faction from what I can tell, then talk to their tech specialist.

You should be able to do it with the Minutemen if you've taken back the Castle.

The possible factions are the Minutemen, The Institute, Brotherhood of Steel and Railroad.

I personally used BoST build it, but a plot twist has made me consider stabbing them in the back. Just saying.

I had a similar, if not the same, problem--for me at least, it turned out that I needed way more power than the power requirements for each individual component added together. They should need 27 power total, but mine wouldn't work until I had well over thirty. Just keep connecting small/medium generators until they power up!

Additionally, check how your wires are connected. I found a glitch where not all of the components would power up if I powered them with wires in between in. Instead, make sure you have a single tower that all of the generators are connected to, and connect wires from that tower to each of the components.

I'm still not entirely sure how power works in the game, but hopefully one of the above solutions fixes it for you.