You need new header pins and connectors. It's important to pair up the wires correctly. One pair of yellow/violet wires will be shorted because they are connected together at the power supply board. The other pair of yellow/violet wires go to the playfield and should not be shorted. Now I don't know which pair go to which side of the relay contacts, but it doesn't really matter so long as the pairs stay together. For example, put the power supply yellow/violet pair to the two COM terminals. Put the playfield yellow/violet pair to the NC terminals.
Oh and before doing any of that you should go to the solenoid test and verify the the relay actually clicks. There should be a test entry that says something like "Playfield GI".