Where is Spawn Unit function implemented? It’s target says self, so I assume it’s on BP_PlayerOneHudTest ?
If it’s implemented in the HUD, you need to call the interface function on the HUD, instead of Player Pawn
You can get the HUD from the Player Controller.
Get Player Controller → Get HUD
This is all assuming BP_PlayerOneHudTest is a child of the HUD class and is set as the HUD in your Game Mode