Please note that different vehicles in the game may require to unlock various squads for controlling them, including vehicles acquired for gold orders, which can be received in the battle pass. New squads and soldier classes are unlocked after reaching different campaign levels.
For example: The vehicle Pz.IV H in the "Invasion of Normandy" campaign is available for the 9th Panzer Division, which is unlocked for level 20 of the campaign, with the new class Tanker II.
You can see in the game which vehicles can be controlled by a certain squad. To do this, select the relevant squad in the "Soldiers" section, and click on the vehicle.