ISSUE: Outlook calendar does not sync in iOS corporate mobile phone but no issue on the computer.

Dear MS Support team,

Asking for your kind assistance on the issue below

ISSUE: Outlook calendar does not sync in iOS corporate mobile phone but no issue on the computer.

Detailed steps of the troubleshooting done:

>Followed Can't sync calendar and contacts with my phone or tablet - Microsoft Support

Go to the Calendar in the Outlook app and tap the three lines in the upper left-hand corner.

1. Customer email accounts "Calendar" is selected.
2. For iOS: Open the Settings app > scroll down and tap Outlook > Contacts and Background App Refresh should be on.>it is on
3. Settings 

   Tap the account that is not syncing > Tap Reset Account.>Done still the same issue.

4. Delete Account > Delete From This Device.>Then re-add your email account Outlook for iOS.>same issue
5. Re-install Outlook and sync the device in Intune still the same issue.
6. Device has no issue and compliant and has the latest version of iOS.

I also made a recording, but I cannot find here how to attach it

We also manage to add the Outlook account under Microsoft exchange and turn off and turn back on the calendar and still the same issue

Thank you and best regards.