Yes, the diff lock is nothing too fancy. Think of it as pressing a pin from one side of diff into a single hole on other side of diff. You have to push on the pin (the lock engagement lever) and then wait, with one wheel slowly turning, until the pin aligns with the hole on the other side. At that point the diff is locked.
So, a little patience; have one wheel moving (spinning), but SLOWLY; once engaged you can speed up some if needed. You have to continue holding down the engagement lever as long as you want it locked. Releasing the lever unlocks the diff.
Also, it may not immediately disengage, (pin gets stuck in hole), if there is continual pressure. Sometimes you need to slow down or reverse direction momentarily to let the lock disengage, sometimes not.
Good luck and hope all is working as it should.