Apple - OSX Calendar not showing Exchange Account

I feel stupid for answering this myself because the "fix" is idiotic.

1. Remove the exchange account
2. Restart the mac
3. add the account back -> everything works.

I hope another answer gets two upvotes if they help someone so they're assigned the bounty I put out on this question. Thanks for the answers!

You could try clearing the calendar cache and see if that resolves it:

Quit Calendar

Go to ~/Library/ by typing ⌘+⇧+G in the Finder and copying that path into the dialog that shows.

In the ~/Library/Caches/ folder, look for com.apple.ical and move it out to your Desktop (it might not exist).

In the ~/Library/Calendar/ folder look for files named Calendar Cache and move them out to your Desktop.

Reopen Calendar

At this point, you might also want to try disabling and re-enabling your Exchange account in the Calendars Accounts pane.

I recently encountered this on a Mac running 10.11 El Capitan. The Exchange account was active in System Preferences -> Internet Accounts and the Calendar was checked to sync, but the Exchange calendar did not show up in the sidebar of the Calendar application.

To resolve this, we deleted the Exchange account in Internet Accounts and then re-added it back in.