Like most Switch titles, you must be on the latest version (1.1.1) to access online features like the Trading Post or the Lost & Found system. Key Features from the 1.1.x Era
While the preceding "Daybreak" (1.1.0) update was a massive content drop, Version 1.1.1 was a surgical strike designed to polish the experience. Pokemon Legends Arceus -NSP--Update 1.1.1-.rar
Beyond the Shiny Charm, the update included minor "other bug fixes" to improve general gameplay stability and online connectivity. Like most Switch titles, you must be on
Because Update 1.1.1 is incremental, it retains all the major "Daybreak" features introduced in 1.1.0: What's the daybreak update? : r/PokemonLegendsArceus Like most Switch titles