Hello,
Followed the link you provided and it all worked fine.
Started by creating new material with Blend Mode set to translucent. Added a color and scalar parameter which I named Opacity and plugged into Opacity in Result Node for the Material.
Below script inside the character/actor you want to fade. This is all based on the link you provided.
When capsule component is being overlapped it will change the original material on the character/actor to newly created instance of the material (1st scr) and using timeline will change the value of Opacity over time (from 1 to 0 over 3seconds).
When leaving the capsule component play timeline in reverse, when complete change back to original material.
End result in [here][1].
