Team Calendar Subscription fails with Office Outlook 365

Our enterprise has recently moved over to Office 365 and we our users are having difficulty in subscribing to team calendars using the ics URL provided for a team calendar.

We are seeing the error in Office "Couldn't open calendar : The action couldn't be completed. The error code is -1" (See attached).

We've also attempted to export to ical functionality in Team Calendars and then attemped to upload the ics file manually but nothing is recognised by O365.

Can you please advise if there is anything we can do from Confluence side to try and get this working?

Thanks