With the new update, each van is assigned a specific "Vehicle Type" like Standard Parcel, Standard Parcel XL, CDV, etc. For your driver to be properly assigned the van on the roster, they would also need to be assigned the van in their associate profile.
YOU SHOULD ONLY HAVE TO ASSIGN "STANDARD PARCEL" TO THE ASSOCIATE.
Please see the screenshots below for an example of Alvin Chipmunk. Notice, CDV VAN 1 is greyed and cannot be assigned
Viewing the details of CDV VAN 1, we see the vehicle type as “Custom Delivery Van”
You can change Alvin’s Vehicles Types in either the Associate Management > Bulk Updates or Associate Management > Associate Details Page
Once that is completed, you’ll now see that Alvin can be rostered for Van 4 after you refresh your daily roster page.