For us, it was the missing entries in Info.plist. Make sure to add the new entries
NSCalendarsWriteOnlyAccessUsageDescription and/or
NSCalendarsFullAccessUsageDescription.
Also, keep in mind, that if you're still supporting older iOS versions (lower than 17), you should also include the NSCalendarsUsageDescription.
Topic:
App & System Services
SubTopic:
General
Tags: