There were three more not voting, and Wyden was there before his scheduled surgery. Pretty cowardly of Manchin.
According to SURVEY USA TV (live steam voting with commentary from the 3-man panel), the ones who showed up knew the cloture vote wasn’t going to pass.
In a cloture vote, not showing up is the same as voting no (for all intensive puposes).
One of the Survey USA commentators stated that Manchin had some big issues with this bill (not to mention Reid trying to cram it down the lame duck congress).