Throwing my hands up on this ignition!

Having trouble getting spark out of my ignition. I have an MSD a high voltage coil and a stock electronic distributor. I rewired it the ignition according the MSD instructions, which eliminates the ballast. A first it ran great. I drove it for while then it no spark. I checked the wiring, and couldn't find any issues. I had another coil so I desided to try it and the car fired right up drove the car a bunch for the next couple of days with no issues. Came out today and again no spark! Tried a different coil still no spark? Wiring still looks good, what I'm I missing here?