The hubs will not lock in when trying to engage the 4WD

More than likely this is the actuator on the front differential. I am attaching the info on it, but we need to check the power on the two wires to find out if the actuator is being commanded on.

https://www.2carpros.com/articles/how-to-check-wiring

Below you will find the location and wiring info needed. If you have voltage when the system is on, then the actuator is the issue.

This is the most likely cause so let's start with this and go from there.

Thanks