Hi Fred,
The mechanism of Outlook for Mac to “read” calendar entries is different from Outlook 2013/2010. And the issue might occur if Outlook for Mac can’t recognize the original format of the calendars. To further troubleshoot the problem, I’d like to collect more information.
1. What’s the email system does the customer use before migrating to Office 365?
2. How did you get the PST file that you imported with Outlook on the Windows computer? (If the issue is related to the PST file, I’m afraid that the only Microsoft supported scenario is that the PST file was exported from Outlook)
3. If the original PST file was exported from Outlook, as you mentioned, please export the calendars to another PST file and send it via the email attachment to the outlook.com account I posted in the private message. I’ll import the PST file to Outlook for Mac on my side to see if the issue persists.
4. If possible, please connect another Office 365 account to Outlook for Mac on the affected customer’s Mac. And then import a PST file to the account on a Windows computer to see if there is the same error on his Mac.
Thanks for your time.
Regards,
David