vehicle is off…does not have any power
When a vehicle is off…it should not have power.
When you say it has no power I assume you mean things like the courtesy lights don’t work when you open the door. Check your battery connections and it would be a good idea to clean them with the battery post cleaning brush, even if they look okay. If that is good then check for power getting to the main panel under the hood. Most everything in that panel should have power on it at all times.
When you say it “does not have any power,” do you mean nothing happens when you turn the key? That means your battery is dead. If the van has been sitting, that’s not surprising. See if it will start with a jump and have the battery tested.