I have the same issue with an error saying calendar response message cannot be sent. I have exhausted all the suggestions here. Calendar turned off and restart. Updated iOS. Restarted phone, etc
Using an I phone SE
When you respond from a calendar entry it sends an email using your default email account, so you need to make sure you have the default email account set correctly, and that it works for sending email. To do that:
If it is specifically a Microsoft Exchange calendar then it should automatically use your MS Exchange email account.
When you respond from a calendar entry it sends an email using your default email account, so you need to make sure you have the default email account set correctly, and that it works for sending email. To do that:
If it is specifically a Microsoft Exchange calendar then it should automatically use your MS Exchange email account.
Have you checked for rogue calendars? See this Apple support link→Delete spam calendars and events on iPhone - Apple Support
or watch this companion video:
I have a massively complicated calendar literally sending 12 or more responses or invites every day and never an issue since I started using I phones in 2016. Apparently in December/Jan I responded to 4 invites (I get the errors in sets of 4 everytime) and this has caused the error that simply cannot be cleared. I believe the address(es) I responded to are invalid but that's a guess. With hundreds of events in the calendar I have been unable to trace out the issue to delete the events. Note I received direct calendar inputs from an unknown source about this same time and these may be the source. I questioned at the time how the heck they were in my calendar without any email etc but blew it off. Now I have this issue persisting since early Jan or late Dec
I will give that a shot - if I have any events not already deleted.
I have the same issue with an error saying calendar response send has failed
