The "Will not win" badge displays below the ads when the algorithm believes you might be dealing with an A/B test that will never produce a winner nor a loser, in which case a new test should be created.

The algorithm for this is not perfect yet, and it sometimes does display the badge even when it's clear that one ad has the advantage, in which case you should ignore the badge.

When not to ignore the badge? When the two ads have enough data and both ads are very close in performance. In this case, if you like how both ads are performing, you can keep both and create a third ad. On the other hand, if you're not happy with any of the two ads performances, then pause one and write another.