getSharedPropertiesAsync is not a function

[MaterCoders]

Hi.

We are facing an issue at one of our enviroments. When a user is trying to open the addin on a shared mailbox . They are getting an issue that getSharedPropertiesAsync is not a function. They are rocking Outlook 365 subscription model .
Office.context.requirements.isSetSupported('Mailbox', '1.13') returns true.
It is exchange online setup. User has Full Access to the shared mailbox.

This is the sample code :

Office.context.mailbox.item.getSharedPropertiesAsync((result) => {
if (result.status === Office.AsyncResultStatus.Failed) {
console.error("The current folder or mailbox isn't shared.");
return;
}
const sharedProperties = result.value;
console.log(Owner: ${sharedProperties.owner});
console.log(Permissions: ${sharedProperties.delegatePermissions});
console.log(Target mailbox: ${sharedProperties.targetMailbox});
});

Office.context.mailbox.item is defined.

Addin has correct permissions and properties added in Manifest.xml .

Am I missing something ?