1. Open the Calendar app on your Mac - if you're seeing your own work calendar, but you're missing a specific shared calendar or resource calendar, first verify that calendar is available via https://outlook.office.com/calendar/.
   • If the calendar you're looking for doesn't show up after clicking "Show All" in the left-hand list, you have a permissions issue that needs to be resolved before there's any chance of it showing up in your Calendar app.
2. Apple Menu -> System Settings -> Internet Accounts -> Look for your work account there (it will probably show up as "Exchange" rather than Microsoft 365)
3. If your account is listed, click into it and ensure that "Calendars" is enabled
4. If your account is not listed, click "Add Account"
   1. Enter your work email address and click Continue
   2. You will be prompted to open a browser - accept and proceed with sign-in from the browser
   3. Once the browser section is complete, close it, and you'll see a permissions screen
   4. Ensure that "Calendars" is enabled
   5. Click Done
5. Open the Calendar app
6. From the menu bar, select Calendar -> Settings -> Accounts
7. Select your Exchange account
8. Confirm that "Enable this account" is checked
9. Close the settings window
10. On the left-hand of the calendar app you should now see a listing for your Exchange account
11. Expand the account (if the details are hidden), and you now should see any resource or shared mailbox calendars that you have access to, and be able to check/uncheck each one to see it on your calendar.