New FCSP's are shipped with old firmware and needs to be updated to the newest firmware prior to pairing the truck with the charger. Since this is a multi day install first priority should be getting the EVSE installed and getting AC power to it. Next you need to connect it to the customer's WIFI and make sure the charger is not used overnight that first day. The new firmware will download and install automatically overnight so when you complete the install the next day the charger will be updated and you will be ready to pair.
Please make sure when installing the Ford Charge Station Pro it is line of sight of the truck for the best customer experience. When you are in the truck you need to be able to physically see the charger from the truck. If the FCSP is located around a corner from where the truck is parked there is a good chance the Home Integration System will have issue pairing or connecting.