Multiple clients disables one's movement?

I have been creating a top down game for a little while now and have just tried to run two clients at once on my PC (through the number of clients option on the play drop down menu) and the second one on the pop up window does not respond to input?

I’ve checked my code and all of my code is that player specific (no get player pawn, only get controlled pawn and the like) so does anyone know what is causing this? And what the fix is?

Thanks.