New wiring harness trouble...

Ok it seems simple enough, I got all new wiring harnesses from year one, dash wiring, engine harnesses, etc. When connecting to the new bulkhead, the engine harnesses are absolutely impossible to get to snap into place, like something is preventing it from going in, but all blade connectors are straight and seem like they are lined up. I am pushing on it pretty hard, but I don't want to break something. I called year one and they said that they are supposed to be a tight connection as they are designed to be water tight. I am stumped here as I cannot for the life of me get them connected. I am making sure I am putting the right one where it is supposed to go as they have the key on the side that you line it up. Any tips? anyone been there? This is on my 67 barracuda. Thanks for any tips.