Calander error message

I keep on getting an on screen pop error message which reads:

Calendar Invitation
your response to the invitation cannot be sent.
OK

*** do I clear this message?

Thanks man

Welcome to the forum.

What version IOS, what device, what is the ISP, what is the calendar you are trying to respond to (Outlook, Apple, Gmail what)? We need more information to be able to diagnose the issue.

Also, please include whatever you have already tried so we don't recommend it again.