Light doesn’t come on, lever moves freely side to side with no mechanical feel
Thanks.
So, the lever should be pretty easy to move sideways, but more resistance to change from High to Low. There isn't a definitive click or feel from the lever for diff lock.
You may also need to drive forward a little way to get it to engage, it may not do so stationary. I'd also be tempted to try it in low as well as high.
If it hasn't been used for a long time, then it might not want to engage at first.
Also worth noting the light may not be working, either down to the bulb, the switch or a broken connection.
With diff lock out, jack up one wheel (front) off the ground, doesn't need to be high, just enough that is isn't touching. You should be able to rotate the wheel freely, you'll be able to see the front prop rotating. Put it in diff lock and the wheel will no longer rotate (it'll still move, but not freely rotate).
If it really isn't engaging you'll need to check the linkage on the transfer box, you should be able to manually move the linkage from under the vehicle.