Looks like Fallout 76 is down across all platforms for the time being while Bethesda does maintenance to apply a hotfix. Last week, the massive 7.5 Patch that brought Wild Appalachia to the game was added, which likely led to the crashes and other update that is mentioned below that this Hotfix is being deployed to correct:
Starting at 11:00 a.m. EDT on Tuesday, April 2, we’re planning to bring Fallout 76 offline across all platforms to perform maintenance and apply a hotfix. This update includes a fix for an issue that could cause the game client to crash and will also address an issue affecting the invulnerability effect applied to Survival mode characters after Fast Traveling or Respawning.
We will let you know as soon as downtime begins tomorrow, and you can return to this thread for updates as maintenance progresses. Please note: There will be no patch notes following this update.
Thank you very much!