In my case it was newly built Ex 2013 box so I spent some time troubleshooting the Exchange box itself, while issue was with the actual user account. In Source he was a member of AD protected group (Domain Admins) which invoked SD Admin Holder to remove inheritance from his account. This was migrated to the Target Exchange 2013. When user saves regional settings in OWA, Exchange tries to save it in AD… and fails. Now it would be helpful if Microsoft Exchange provided some more descriptive error here (like Access Denied), but OWA just re-loads to the same page. What gave me an idea is trying to set his regional settings in PowerShell:
Set-MailboxRegionalConfiguration -Language En-Us –TimeZone “Eastern Standard Time”
It fails with: “There was a problem accessing Active Directory. Check your network connection and try again.” Very descriptive, right? 🙂 Finally noticing that user account has inheritance disabled. Enabling inheritance on the user fixes OWA and above command-let completes successfully.
Users with disabled inheritance are very common headache during migration. Aside from described here OWA issue, I have seen Active Sync failing on such users and some more not-so-nice side effects. Be careful – every QMM Full Re-Sync disables inheritance again. And sometimes fixing it in Source is not an option either. So I often schedule PowerShell script to be executed once a day which pulls such users and fixes inheritance.