Hello!
I’ve noticed that using Lens Flare will not work with deferred rendering: when launching the application, the flare will not appear.
Is it a bug or I’m doing something wrong?
Cheers!
You’re doing something wrong. Try using one of Unity’s default flares to see if the problem persists. Also, the lens flares post processing effect doesn’t work, so place it on your light instead.
I’ve done all that, but the flare does not appear 
I used the default flares only and placed the flare on the light.
Using deferred will not show the flare, while switching to forward will show the flare.