Icloud Calender sync Error for some events

the server answers with an error: unauthorized for some calender syncs

emails receiving and sending works but not generating some events in the calender sometimes do not work some do work…

the problem seems with yearly recurring events …

This is a server error.

First the server allows you to access the folder, then immediately is says you can’t.

You will need to contact the provider for assistance.

Provider ?
Apple Icloud Calender? why and how works on the iPhone, Mac…
Internet provider?