Newbie Water question

So it finally stopped raining long enough. I got out the book and looked over winterizing. Couldn't find anything I hadn't been over with the book before. Hooked up water and set the winterizing switch to normal, water service station to normal and turned on the water. It sounded like it was filling up, the kitchen faucet was open. Closed that and no water coming out the flapper. ran the water through the kitchen and shower and still no water. After watching the tank levels get to the first light, still no water. All seems well. I ran the grey tank water out on the lawn and it emptied the tank fine, level is back at zero. Not sure what is different now from the first three times I tried this but it seems ok. So my appointment on the first will now be for belts, hoses, fluids and brakes. I'll remind the service center on the Sprinter oil specs but they're qualified service center...surely they wouldn't use the wrong filters/fluids.
Thanks for the comments. It's good to know we aren't alone with our problems.
Safe travel.