I just installed a Maestro ELV dimmer connected to a LED ELV-compatible fixture (WAC lighting).
The fixture does not dim however, it is 100% on at all dimmer settings and shuts off when the dimmer is off.
Any thoughts of the cause?
This sounds like you fried the dimmer's AC-chopping element to the point where it's simply a short circuit, while the internal mechanical switch is still able to turn the light on and off.
At this rate, I'd start by replacing the dimmer as the first port of call.