Unable to screw through plaster and lath wall
Best case is you've probably hit a concrete structural wall.  In that case use a hammer drill and cement screws or anchors if you really need more support than you get from the 1.5" in front of it.

Worst case is you're hitting a conduit or water pipe, in which case thank goodness you haven't managed to puncture it.

I'd look for a work box or some access where you might probe the wall to determine what's back there.  If it's the former case you'll see that.  If you don't see a cement backer then carefully drill probe holes around where you were trying to screw and see if you end up to one side of the thing you shouldn't be hitting.