This is due to the fact that game sessions become available only at a certain time.
Developers open access to Fallout 76 for only a few hours a day, and this happens simultaneously for players from all over the world. And since Bethesda, logically, adapts to US users, this is inconvenient for Europeans.
So, the first testing session took place on October 24 from 2:00 to 6:00 Moscow time, when many European players simply could not find an opportunity to play.
Fortunately, Bethesda has responded to the problem, and will hold two game sessions over the weekend, targeting different time zones: October 28 at 0: 00-2: 00 and at 19: 00-21: 00 Moscow time.
Note that the beta is currently only available on Xbox One. PC and PlayStation 4 owners will have to wait until October 30th.