How use/test replication in two different methods
If you want test replication from the Title map (ACS_Map_Title) you should use "Standalone" mode because the host will going to be the one who clicks the "Host" button and not the first PIE by default
In this map, only owning client can access her own widget.
This method are used if you want each PIE select her own Party Account Mock (with her own UID)
If you want test but in the test map (ACS_Map_Test) you can only test with 2 player because you don't select UID and i do UID selector depend if it's Server or Client (so only 2 ways)
And more, you must run this at "Play As Listen Server"