How can I get back to turning on and off the light with both switches?
Wire it correctly.
Both the dimmer and the sw have 3 terminals (or wires on the dimmer)
On the switch it is marked common and is a darker color.
On the dimmer it is probably black with the other 2 being red.
Look in your sw boxes. You need to identify the common wire in each of them. That's why I saked the wire colors earlier.
There are several ways that it could be wired. The easiest way for YOU is to look into the box and see which TWO
of the 3 wires wires go together into the 3 wire cable
. The common will be the OTHER
The common wire goes to the common terminal or pigtail. The other two are interchangable.