New dimmer doesn't dim
I recently replaced an older dimer (likely mid to late-1980s age) with a new Leviton slider dimmer (model IPI06). This is a three way switch and the dimmer controls the light fixture on the ceiling fan. A second switch in the box controls the fan, and a second set of switches in an adjacent room independently control the same light and fan.
I wired the new dimmer in and it will turn the fan light on and off, but will not dim, even after I followed the instructions and used the small dimming adjustment screw.
I have a basic knowledge of wiring and the instructions included with the dimmer are not the greatest. The box contains a ground (green), white, black, and red wires; the dimmer has two reds (one of which is used only with a 3-way switch), a green, and a black. I connected the two blacks, the two greens, two of the reds, and the box neutral (white) and the second red wire. After no dimming, I switched the two reds from the dimmer around and got the same result. Trying to avoid calling my FIL (he's an electrician). Any ideas here?
-Daryl, learning how to keep up with an 80 year old house in PA