Custom Branding Sign In Page does not come up

We had to manually install a VPN client on the Autopilot devices for prelogin to work. I do not see that the custom branding page appear so that we can have the user login to the device with their user credentials. What could be the reason. 

These computers came from the vendor and the hash was uploaded to our Microsoft Business Store sometime back. Unfortunately, we are starting to get this prepared to ship it to the customers. I am not sure why it would not get the custom branding page for user to logon even though we have a Deployment profile, the device is added to the profile and users added to the Hybrid AAD join group etc... Everything is setup and the device shows it is registered. Any thoughts please, Need some immediate help to fix this.