I have a 2014 Winnebago and had the same problem, I could not get the hose to connect with the connector. So I had it replaced under warranty. The replacement unit is doing the same thing. I did get it to connect once before the warranty repair. Sooo, I come to the conclusion if there is ANY back water pressure on the connector, just use a small screwdriver/hammer and lightly tap the center of the connector to release the pressure. Then I could insert the coiled hose connector.
I hope this is your problem, if not - SORRY!
Harold/Cynde
2013 Ecoboost 4x4 with a 2014 Winnebago Ultralite