My vehicle Make is missing from the drop-down box in VinMotion when I try to add the vehicle.

If you are trying to select a make in VinMotion that is not in the make list on the vehicle details page, at the bottom of the list there are two options, Other and Load All Makes. If you choose Load All Makes, then some more uncommon makes, such as Freightliner, will load. If you choose Other, then you can type in a Custom Make. If you get a call with this issue for a vehicle the customer regularly stocks, submit an enhancement request to get the Make added.