Hi @ChrisMyers_NewQuest . Thanks for sharing the details for this issue. As we discovered, the Illustrator file that you were trying to sync layers into was about 2 years old, which may be the cause for this problem. But you were able to create a new Illustrator file with the same data, and then sync new layers to the newly created AI file. We also discovered that your map was pretty large in physical size, so the sync took a few extra moments.
We discussed some steps to alleviate recurrance of this issue:
1) Maintain a webmap that contains the layers your organization uses for this commonly reproduced map. This will allow you to quickly recreate an AI file with the several layers in case an AI file becomes "unsyncable." Especially with the passage of time as files age. Also, this will allow you to quickly create maps at other locations, extents, and scales with this same data.
2) PPI < 100 for maps containing only vector will often make syncs - and any subsequent syncs to an AI file faster. Not the root of this issue, but noted as one of the reasons for longer syncs. Syncing at 300 for vector-only files can add unnecessary size to the files, especially for one as large as yours.
3) the team will look into longevity of AI files. However, it would be good to follow step one as files do get corrupted over time, and Illustrator and Esri constantly push updates. Files will become less compatible over the years.