iPhone Receives Calendar Invite, but does not put it on the calendar.

Daughter's calendars are not showing invited events on her calendar even though they show as accepted on my end. When she clicks on "Accept" on her emailed invite, she is asked : "Open with: Chrome, Google, or Safari." Tried Chrome and Safari, and each shows the calendar date and "Accepted" at iCloud.com. Both phones are up-to-date with iOS 16, but this has been a forever problem on all iOS versions. Someone else had this problem posted (with 47 me too's) in 2020, then made a post that some "savvy iPhone person" remedied the problem. Unfortunately, the person did not post how it was resolved. Can someone help?