Why does an LED effect work in one sim but not another?

Every DNR LED effect is drawn from telemetry the sim publishes to SimHub. If a game does not report something, no plugin can light an LED for it, so an effect can be perfectly configured and still never trigger in that title.

The cases the plugin flags on screen:

• TC Active in iRacing, the effect that fires while traction control is actually stepping in, requires the third party Dahl SimHub plugin. Without it, iRacing does not expose TC activity.
• ABS Active in iRacing, the same thing for the anti lock system, is not available at all, because the game provides no such telemetry.
• Both of those are about the aid stepping in. The setting your TC or ABS dial is on is a separate thing, and iRacing does report that. Rotary rings, Car Ranges and the TC and ABS readouts all work in iRacing with nothing extra installed.
• Lift and Coast is only available for Le Mans Ultimate.
• SC Delta, the safety car delta animation, is for the EA F1 series.
• The flag box pit box countdown is iRacing only and needs the third party RomainRob SimHub plugin.
• iRacing pit service effects such as Fast Repair and Tear Off exist only in iRacing.

More generally, hybrid effects need a hybrid car, rain light and wiper effects need a sim that reports them, and spotter accuracy depends on the position data the title provides.

DNR supports Assetto Corsa, Assetto Corsa Competizione, Assetto Corsa Evo, Automobilista 2, the F1 games, iRacing, Le Mans Ultimate, rally titles and BeamNG.drive, plus an Any game setting for everything else.