Hello,
I´ve followed this tutorial: https://docs.unrealengine.com/latest/INT/Videos/PLZlv_N0_O1gYDLyB3LVfjYIcbBe8NqR8t/5HkghxEIXiU/
and after I´ve attached the anim trail and started the game, it became clear that the trail is only rendering when the player moves from right to left. I have attached two screenshots for a better understanding.