Raintree's page

Rules: Encountering a Card, p.10. wrote:

If multiple checks are listed on the card with “or” between them, choose one of them. If there’s a “then” between them, you’ll need to succeed at both checks sequentially to defeat the bane; you must attempt both checks, even if you fail the first (because failure often has consequences). “Or” takes priority over “then,” so if a card says “Wisdom 10 or Combat 13 then Combat 15,” you must first attempt either a Wisdom check with a difficulty of 10 or a Combat check with a difficulty of 13, and then attempt a Combat check with a difficulty of 15. Any character at that location can attempt one or more of the checks, as long as the character who encountered the bane attempts at least one of them. If the character who encountered the bane is not able to attempt at least one of these checks, the bane is undefeated and other players do not need to attempt checks against it.

Multiple characters may not attempt the *same* check. And the bane isn't undefeated until all of the required checks have been attempted.

If the "bane isn't undefeated until all of the required checks have been attempted.", why does the rule says, "If the character who encountered the bane is not able to attempt at least one of these checks, the bane is undefeated and other players do not need to attempt checks against it." If the player is unable to attempt and other players do not need to attempt surely the bane is not undefeated. What happens then?

In what kind of situation is active player unable to attempt at at least one of these checks?