Just a heads up - Microsoft Defender for Cloud Apps is incorrectly blocking multiple legitimate domains, certs, and cloud apps. Microsoft's issue ID is DZ1231199 (https://admin.cloud.microsoft/#/servicehealth/:/alerts/DZ1231199).
More discussion on r/sysadmin subreddit here:
https://www.reddit.com/r/sysadmin/comments/1r30bz8/get_it_together_microsoft/