https://www.gamespot.com/articles/fallout-76-has-no-cross-play-support/1100-6461172/

Fallout 76 takes the franchise in something of a new direction in that it's an always-online, multiplayer-focused game that encourages players to work together or compete. There won't be cross-play for any systems, however, Bethesda's Pete Hines said on Twitter recently.

Game director Todd Howard already talked about how Sony was to blame for the lack of cross-play support. Hines didn't mention Sony by name, but said "there are a number of reasons" for why there will be no cross-play support. He did not elaborate.