That accounts link is specifically referring the Destiny Game Content through the mobile app. Wait until the tomorrow when the beta goes live again and give it a refresh!
I have this issue as well. I have been playing since the start of the Xbox One beta and it says I have no accounts linked. "No Accounts Found. be sure your account is linked on Bungie.net." "tap to try again"
Verify that the correct account is linked to your bungie.net user profile though your [url=http://www.bungie.net/en/User/Edit]Settings[/url] then Account Settings. You MUST be on the same account as you're playing Destiny on. Otherwise, you may be accumulating stats, but under a different bungie.net user profile.