I was able to solve the problem on both my iPhone X and iPad. The error was being generate by my Exchange account. I went to Settings->Accounts & Passwords->[exchange account] . I then switched off the calendar, chose to delete it from my phone, and finally switched it back on. No problems since on either device.
I'm still having the error several times a day. I downloaded the new ios 11.1.2 and still getting the error. Very frustrating and I wish Apple would address this issue.
I never had this problem until 1 week ago when I installed 11.1.2. Highly annoying as it occurs multiple times per hour. Apple - please fix ASAP.
I tried all of the above, I restarted the phone - but nothing helps. It's so annoying..
I'm still having the issue also. I would hope that apple would step up to the plate by now!!!
My phone just started this same message today! I upgraded a week ago! Nothing I’ve read from others works!
So glad you were able to fix the issue...must be for new iphones as it still is not working for me and becomes more annoying each day.
This worked for my iPhone 8. Thank you!!!
It worked! Thank you SO much for posting this. Solved months worth of annoyance.
Thanks for feedback, its resolved my issue by turn off and on from calendar on my exchange account .
Much appriciated .
Thanks
This started happening the day I shared my O365 calendar and two members of my team shared theirs with me... aggravating issue that needs to be resolved!
Calendar Invitation Error
