Hi @David Steer
As a workaround, I suppose you can use the classic EAC instead to export contacts.
It can be accessed either via the new EAC:
or via this url directly: https://outlook.office365.com/ecp
In the classic EAC, please locate recipients>contacts.
You can select all contacts and export them to pst.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.