If you have a multi-gang dimmer (2/3/4 gang) you must make sure the MASTER 1 module (viewed from the back) is always connected and loaded in order for the other gangs to operate. The RF module is located in MASTER 1.
If you look at the dimmer from the front, you must make sure the right hand gang is loaded and connected so you get an Amber LED illuminated, then go ahead and wire the rest of the gangs.
The RF module is located in the far right gang. You must see amber or Blue LEDs on all gangs.