Battlegrounds missions are not part of the expansions, but are instead part of a specific season, which is why you are seeing that message regarding Season of the Chosen. Owning the expansions does not necessarily mean that you own the seasons, which is part of why the question was asked as to what exact expansions and bundles you had purchased. While you say that you own Beyond Light, you have neglected to verify the exact version of Beyond Light that you purchased. Only the Beyond Light Deluxe Edition contained multiple season passes. The basic version does not include any passes. The Legendary Edition, which included Forsaken, Shadowkeep, and Beyond Light; comes with one single season, which will unlock the season active at time of purchase. As your Bungie profile is private, we cannot view your game history, see your characters, or even see what platform(s) you may play on. The only way that we can provide assistance, is to ask for the necessary details, to try to pin down what the issue may be. Customer service staff would need to ask all of these questions as well, in order to determine what may, or may not, be the problem. If you did not specifically purchase the Beyond Light Deluxe Edition, or purchase Season of the Chosen in-game with silver while it was active; then you will not have access to that seasonal content at this time. The game will direct players to purchase the Deluxe Edition, in such cases.