Hi Fred,
Sorry for the misunderstanding.
I checked the private messages and found you haven’t provide the private email address I collected. Have you tested the issue with another new PST file?
In addition, I imported the PST file you provided to another newly created Office 365 account and reproduced the error. But I found that the calendars can be edited and synchronized between OWA and Outlook for Mac properly.
Currently, for the sync issue you mentioned in the original post, could you provide the following information for further troubleshooting?
1. Please provide more detailed descriptions about “subsequently he is having sync issues between the calendars on his two Mac computers”. Does the issue occur to all calendar items after the importing or just the imported calendars?
2. Can the calendar changes made on Outlook for Mac be synced with OWA properly?
3. I noticed you also did the test with your own Mac. Does the sync issue exist with your Outlook for Mac?
4. Does the issue exist between Outlook 2010/2013 on Windows computers?
Your patience is appreciated.
Thanks,
David