I got this MH-50X-Q-KIT Keystone ballast. It is multi-tap so I am using 120 V. Power is going into the ballast. There are two Com. wires right next the each other on the larger winding side, one is going the CAP. the other the neutral from the source. The other side of the CAP. runs back to the ballast using the (CAP) lead ( factory wired). the other two leads . the X-3 and lamp neutral is going to the lamp. I fired it up and nothing ( There is no Ignitor) There is 120 going in but only 3V going out. Any insights or thoughts. Thank you.

I don't know what ballast you're using, and I'm in the UK anyway where things work a little differently, but if you have a 50W MV lamp then you need a 50W MV ballast for it, MH isn't compatible. That works for most discharge lamps most of the time. There are occasions when they'll work for other types of lamp, for example here MH and HPS are pretty much the same (but not always) but as a general rule, the ballast and lamp should match.