Oracle Apex - writing a sentry function, getting session timeout immediately after connection.

Apex 21.2 running under Windows.

I'm writing a sentry function which uses a token past via the URL and creates a session for the user associated with the token. That data is retrieved from the database using a select run under the APEX_PUBLIC_USER. The URL has server and port, application, page, and 1 parameter

The URL also contains the page number of an Interaction Report.

Once the user is validated, a session is created for the user by calling APEX_CUSTOM_AUTH.GET_NEXT_SESSION_ID, the function returns TRUE and the report is displayed.

However, as soon as I modify any of the attributes on the report (for example number of rows displayed), I recieve an error - "1 error has occurred. Your session has ended"