Anyone can change a proposed match to an "unmerged match", and without any comments as to why. And it may or may not be one of the profile managers.
By the same token, anyone can "delete" an unmerged match, and re-propose a match, which restarts the 30 day clock toward default approval.
Gaile's suggestion is good... ask the current profile managers if there's any known reason why it should not be merged. Otherwise, make the necessary changes to resolve any differences, and re-propose the merge.