During test server I had this issue.
Now Unity is live and I have this issue.
The game basically stops trying to load. No error messages. The page loading animation stops.
I've cleared browser cache. I've cleared browser and windows DNS. I've used THREE DIFFERENT BROWSERS. I have all ad blocking turned off. I accept cookies for Ubisoft.
I couldn't play using the last version of the client and was told Unity would fix things.