Hi Douglas,
This issue was posted to the Service Health Dashboard (SHD) as incident SP89334 starting at December 26 2016 3:00 PM (UTC). The user experience of this incident is: Users may be unable to access SharePoint Online sites.
Tenant administrators can view current information and updates on SHD at the link here:
https://portal.office.com/admin/default.aspx#@/ServiceStatus/ServiceStatusHistory.aspx.
If you are experiencing a similar issue and do not see an SHD post, please let us know by sharing your tenant information viaPrivate Message (PM) as this may indicate either a scoping issue or an independent problem.
For affected customers to easily identify the information here, this thread will be closed. You may subscribe to this thread or refer to SHD for updated information. I will also post back here once the issue is resolved on SHD.
Thanks,
Sheen
[Updated by Sheen V. Ali MSFT, 26 December 2016, 7.11 PM (UTC)]