There is a delay in syncing emails due to Gmail API failures. The affected users are seeing a delay in the emails synced. Gmail has confirmed there is a disruption in the service and that they're investigating.
(https://www.google.com/appsstatus#hl=en&v=issue&sid=1&iid=ebde53dc07f139712e8269e0f523e6cb)

Google has updated that the problem has been resolved. We're waiting for the sync to recover.

We believe this issue has been resolved. Thanks for your patience. If you see anything unusual please don't hesitate to contact us over at hiverhq.com or via email at support@hiverhq.com.