I have a user that for some reason, he keeps getting old reoccurring meeting invites showing up on his iPhone calendar. These meetings have either long since been canceled, deleted or declined. If he tries declining the series, He gets an error "Calendar Invitation - your response to the invitation cannot be sent".he has also tried deleting the account off the phone, restarting the phone and adding the account back, but it does not solve the problem.
Desktop Outlook, outlook 2016 does not have this issue.
Thank you very much in advance!
Figured it out. Thank you all!