4WD Won't engage, '96 K1500 Suburban

['72 Chevy Suburban]

My truck is in 2HI and when I push the button for the 4WD Hi or Lo, the light flashes, but nothing happens. Here is what I have done:

Checked the 4x4, trans and TC fuses and all are ok
Per the FSM, checked to make sure all lights come on for 1 second during startup

I followed the FSM through the troubleshooting up to Table E until I got to DLCs and DTCs and that is where they lost me.

There is a normal sounding clicking noise coming from under the dash and I assume that the TCCM is operating. By process of elimination, does this mean that it is probably the Actuator(?) that is located on the transfer case?

Is there more troubleshooting that I can do in order to further narrow this down?

Thanks,