@B.Will Thank you so much! Joining the orange and black with the black wire on the HS200 worked.

@B.Will here's the wiring for another switch in another room for comparison

@B.Will Thanks - could you clarify if I should disconnect the orange wire and then join the yellow and black? The orange wire was not protected with a wire nut.

@B.Will Here's a photo of the old switch. Black and yellow wires were connected to it

I'm trying to install a TP-Link HS200 smart switch... The yellow wire was originally connected to the old switch and the orange wire wasn't connected to anything. If I connect the yellow wire to a...