Problem
"After accepting or declining a meeting, using the Apple mail app on my iOS device, the invite seems to get stuck in a loop."
Solution
This is a known Apple issue. You will need to remove your Cal Poly account from the Mail app then re-add it.
Go to Settings > Mail > Accounts > tap on your Cal Poly account.
From the bottom of the screen, tap Delete Account.
When prompted, tap Delete from My iPhone.
Lastly, you will need to re-add your mail account. See Set up Outlook under iOS.
For the best experience, use Microsoft’s Outlook app instead of Apple's Mail app to accept or decline meeting invitations.