Yesterday was a big day for Fallout 76, as the second major patch since the games release went in bring several improvements that players have been clamoring for. However, it wasn't all Carrot and Soot Flowers, as the update took over 5 1/2 hours to complete and then this little snag hit PC players once it was complete:
Per the Bethesda official site, here are some additional details and instruction on the Hotfix so you can apply it if you do not have auto-updates engaged:
We've just released a hotfix for PC in order to reduce crashes that players could encounter upon loading into a world following today's patch. There was no maintenance for this update, but PC players will need to download a small patch, approximately 14MB in size.
To download this hotfix, please completely exit Fallout 76 and your Bethesda.net launcher should begin updating. If it does not start the download, please use the "Check for Updates" option found under "Game Options" near the top right corner of the launcher.
Finally, today's hotfix has updated the game version on PC from 184.108.40.206 to 220.127.116.11. If you are unsure whether you have the latest version installed, click "Settings" from the Main Menu, and you should see 18.104.22.168 near the lower-left corner of the screen.
So it appears this was a minor issue, but until you download the update and apply it, you are still susceptible to the crash.