Although Bethesda is saying "some" of its users experienced a weird bug yesterday that re-downloaded the Fallout 76 B.E.T.A. My guess is that it was more than some, and more likely most or many of the PC people that logged on at 7:00 pm yesterday to unlock and start playing. Instead, the game proceeded to try to re-download, and with servers getting hammered, basically rendered PC players unable to jump in before the session expired at 11:00 pm EST, including one of our own.
Fortunately, Bethesda immediately posted a note that the B.E.T.A. would have some new hours to compensate, s they extended the Thursday 11/01/18 time frame (originally 2-7pm EST) to 2pm - 11pm EST. So that covers the lost hours from last night, but with the bug not fixed yet (so far) and PC players not happy, I am not sure that having to wait a couple more days to get their time in will mend the broken trust from Bethesda.