We've pushed out a fix to get these syncs running successfully. All looks good though we'll continue to monitor for a bit longer to be on the safe side.
Posted 5 days ago. May 14, 2019 - 10:42 EDT
We're working to resolve of an issue impacting manual syncs for a handful of App Store Connect accounts as well as syncs for newly linked App Store Connect accounts. We'll have a fix rolled out shortly!