The approval window was cancelled

Closing the popup or declining the request sends you back without finishing the connection.

An old connection attempt was reused

If you reopen an older callback page or retry from a stale popup, Meta may reject the attempt.

Browsers with several Facebook, Instagram, or Meta sessions open at once often end up using the wrong account during login.

Complete the approval popup instead of closing it halfway through.

If you were bounced back from an older attempt, start over with a fresh connection instead of retrying the old window.

Make sure the Threads profile itself is active and accessible in the signed-in account.

If the problem only affects one browser session, sign out of other Meta accounts and try again.

If the currently signed-in Meta account does not own the Threads profile you expect, the connection can fail or attach to the wrong profile.