I read through the
WfV instructions for authors (out of curiosity) and whether they can make work for Whispersync depends on whether the audio narration was done word for word. If any changes are made to the uploaded text or audio files, like fixing formatting errors, the Whispersync feature may not work until they can be synced again. It also looks like, for example, using foreign characters like Greek or Cyrillic mean the audio and text cannot be synced for WfV.
Edited - I "bought" the free version of 1632, and even though the Audible book is said to be available for $2.99 through WfV, it does not show up at that price on Audible.com. When I looked at my WfV matches on the Amazon.com website it also does not load in the list. Never had that problem before.