Single player horde mode locked to I7???????

The single player horde mode seems I7 locked? I have two machines one an i5 4690 another an i7 6700 and have two vives, one(I7) has single player horde mode the other(I5) does not! Cant think of why this would be.... Why is this when both machines seem to run the game at full specs fine? Could use some developer feed back here.....