Many users took to Google's support forum, Reddit, and AOSP tracker page to report the issue on their Nexus device that was resulting in late or missing notifications for Gmail and other Google apps and services. The volume of complaints hinted at a widespread outage. A Nexus Community Manager on Tuesday said on Google's support page, "Thanks again for your patience on this while the team investigated the issue. I'm happy to announce that a fix has started to roll out. This fix requires no action, and will roll out globally over the next week."
Gadgets 360 had independently confirmed the issue as we faced a similar issue on a test Nexus 6 smartphone. Notifications from Gmail occasionally took hours before showing up on the device. Several Nexus 6P users had also reported the issue. It is worth mentioning that not all users faced the issue. Many users had noted that disabling Gmail and some other Google apps and services from Androdid 6.0 Marshmallow's battery optimisation feature apparently fixed the issue.
Last month, Google rolled out the v5.10 for its Gmail app which fixed a sync issue involving Hotmail accounts.
Google, earlier this month, announced that its email client, Gmail, was also used by more than one billion active users worldwide. Google CEO Sundar Pichai shared the news with investors and media at Alphabet's earnings call and added that Gmail hit the milestone last quarter. To recall, Gmail had 900 million active users as of May 2015.