If your Publishwide Sync App is not syncing a marketplace that you selected, it is because the marketplace was de-selected.
When the Publishwide Sync App encounters an unexpected error during sync, the marketplace that causes the error will be automatically de-selected. The next time an automatic or manual sync is triggered, that marketplace will not be synced.
To re-select the marketplace:
Open your Publishwide Sync App
Click on the "Settings" in the lower right hand corner.
Click on the top button that says Settings
Click on the Platforms button
Click Next to go through and select the different platforms
If this error repeats itself, please send us a copy of your logs and also contact us.