I've got a user with a Mifi 7730L who for some time has had a variety of problems with her Office 365 Sharepoint/Office Online, Outlook, and Skype for Business.
She mentioned in passing that her Outlook 2016 and Skype take about 10 minutes to connect after she called to report that opening a spreadsheet saved to her Sharepoint-based Microsoft Planner in desktop Excel would freeze with Excel at the splash screen with the message "contacting server". As we discussed this and some unrelated issues, after about 10 minutes, the spreadsheet finally opened.
Interestingly, and why I think the problem is with the Mifi 7730L, is that when she makes a VPN connection to the headquarters office, Outlook and Skype connect immediately, and opening the spreadsheet from planner happens in about 10 seconds, not ten minutes. She told me she typically connects the VPN first before opening Outlook and then afterwards drops the VPN connection and Outlook continues to work.
I also identified that when running the Outlook Support and Recovery Assistant it took an unusually long time to complete the initial authentication-related steps after the user signed in.
I preemptively disabled IPv6 on the user's laptop and rebooted. The Mifi 7730L also has IPv6 disabled. Is there anything we can do to get the Mifi 7730L and Office 365 to work together smoothly? Should she call Verizon tech support to resolve this?