Hi Layne,
If you just imported data into your Outlook for Mac client, it may take some time to get every ready, so I recommend you wait for more time an checked to see if the issue persists.
If you’ve set up it for more than several days and the issue happens, I suggest you contact our Outlook for Mac support for dedicated support, since we only focus on Office 365 Online service on the forum. Our engineers on Outlook for Mac forum are specialized in Outlook for Mac client issues, so you’ll get the most professional assistance there. Thanks for your understanding.
Thanks,
Vivian Wang