https://wccftech.com/fallout-76-beta-availability-gameplay/

Later this month, all those who have pre-ordered Fallout 76 will be able to take part in the game’s BETA. Unlike other betas, which are available at all times for a few days, the Fallout 76 BETA will not be available at all times during the testing period, something that might prevent more than a few players from enjoying it. Bethesda’s Pete Hines recently commented on the matter, and what he said is definitely good.

Asked about the BETA availability hours, Pete Hines confirmed that they will make sure to make it available at reasonable hours, avoiding school and work hours.