Exchange 2010 to 2016 Mailbox Moves - One user can no longer see Calendars

Question

So we've just finished moving all of our users to Exchange 2016 Databases. This has gone fine, except one particular user suddenly can no longer view other people's calendars. It's just this one user to our knowledge, and it doesn't matter who he tries to open, everyone's calendar says "No Connection".

I checked Outlook Connection Status - All was good, even the connections to the calendars he was trying to open
Recreated Outlook profile - same issue
Cached mode vs. no cached mode - same issue
Tried on a different machine - Same issue
Tried on a different machine with Outlook 2019 (vs 2016) - Same issue
Forced his machine to access Exchange CAS Server directly (vs through Kemp Load Balancer) - Same Issue.

The Kicker - Tried using Outlook Web Access - this WORKS!

Also, I can open his calendar no problem.
Also, he can open ROOM mailbox calendars no problem.
He can open shared mailboxes (Full mailbox contents) No problem.

Answer 1

Well I started working with the user to replace his mailbox. We setup outlook auto archive to put everything older than 1 year into a PST so we wouldn't otherwise have to deal with it. And once that process finished, now he can suddenly see everyone's Free Busy.

So obviously some corrupted mail or calendar item causing grief.

Answer 2

Glad you have take such steps for troubleshooting, but still missed some, test the following scenarios and see the results:

1. Remove the permissions and re-add permission in powershell for him, if you were using those calendar-specific permission, try full access this time.
2. Restart Outlook in safe mode. Found a similar issue results from an add-in named "icloud for Outlook".
3. Test Outlook autodiscover. Press ctrl and right click outlook icon, select "test Email autoconfiguration" and tick "use Autodiscover" for test.

Reference link: Outlook Shared Calendar shows no conenction - Resolution with screenshots
No Connection error on Shared Calendar
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

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Answer 3

Hi

Compare permissions on a calendar to his calendar. I saw similar behavior with migrations from exchange 2010 to Exchange 2016 and had to go in and modify 1 or 2 users. cannot explain why it happened.

Answer 4

Thanks for the feed back. I did some investigation and here's what I learned.

1. Outlook safe mode didn't help, I was hopeful it would, but it didn't.
2. Autodiscover test seems healthy.
3. This seems to be related to free busy only. I went and granted him Author permissions to my calendar, and it went from "No Connection" to suddenly seeing all my calendar items and details.

When I removed the permissions (and cleared his cached OST file) he went back to seeing "No Connection" on my calendar. Default is granted access to my Free/Busy. So Granted him access to my Free/Busy specifically, but that didn't help.

Free Busy info sharing seems to be working for everyone else in the company, at least everyone I've checked with.

Answer 5

Thanks Eric,

I'm almost at the point of doing a replacement of the mailbox.

For the mailbox repair, there are many different options for corruption type. Do you know which would be most applicable?

For the MFC MAPI where you suggested checking the permission on that folder, which folder did you mean exactly?