This problem occurs with auto and manual sync mode and it is unclear what the cause of the incident is. On its support page, Google said it is actively investigating the source of the bug and what the company can do to fix the problem.
" There are many stages in the investigation, including error correction, isolation, diagnosis and currently we are in the testing phase ," Google said. If you are also unable to sync email on your Android device, please wait patiently. I will continue to update when there are newer information.