That could be due to various reasons:

Intensity of the light is too low.

The light is way out of the view.

To troubleshoot this we suggest you move your light source into the centre of the camera view and then tweak the intensity until they are visible.

Yes, this will work with any render engine since the plugin has its own separate render engine which works in the compositor. You can therefore use it for VFX as well!

What sets this plugin apart is that it doesn't merely replicate lens flare effects artificially; instead, it optically simulates them using a specially designed integrated render engine. This approach enables you to attain the most authentic and physically accurate lens flares possible.