I like many others have been struggling to host on Ubisoft Multiplayer and am getting the Latency 999 and nobody can enter your game.
I have spent most of the week on this with all different settings for Router and Security software all to no avail. However I found a fix that worked for me.......
Do not use any automatic password imputter for the Ubisoft Forum. Disable it. It seems to me that when you set up a game, then the automatic password provider that you use to gain access to the forum also kicks in and a conflict occurs.
I switched mine off and now am able to host with no problem.