Xero XPM API - Get Current Invoices 401 Response

We have been authorised to access the Xero Practice Manager (XPM) API and have run the OAuth authentication flow successfully.

I am trying to retrieve the list of XPM current invoices as detailed here: https://developer.xero.com/documentation/api/practice-manager-3-1/invoices/#get-current

When I make the call:

https://api.xero.com/practicemanager/3.1/invoice.api/current 

as per the documentation, I get a 401 response code with response payload:

{"Type":null,"Title":"Unauthorized","Status":401,"Detail":"AuthorizationUnsuccessful","Instance":"91d7...40f","Extensions":{}}

As mentioned above the OAuth authorisation flow succeeds and the user has all rights available within XPM itself. And, calls to other XPM endpoints return data as expected, so I'm confident this is not a straight permissions issue.

To me it seems like it is likely a scope issue, but the scopes specified in the authentication flow covers all the XPM scopes listed in the documentation: https://developer.xero.com/documentation/guides/oauth2/scopes/#practice-manager-account-scopes

offline_access practicemanager.client practicemanager.job practicemanager.staff practicemanager.time

To summarise:

• The user that performs the authentication flow has full rights within XPM
• The OAuth authentication flow succeeds
• All (documented) XPM scopes are included in the auth flow
• Other XPM API calls succeed
• Attempting to retrieve data from the XPM Invoices endpoint fails with a 401 error

Is there something I missing here? How can I retrieve data from the XPM API Invoices endpoint?

Any guidance very much appreciated!

Response received from the Xero Support team.

The scope needed to be amended to include the base "practicemanager" and/or "practicemanager.read"