Get absences or periods present/checked for student #84

Hello,
I'm trying to make an API call to get information on whether a student was present on a specific day.
I am successfully calling

the WebUntis API endpoint
GET {{EAP_URL}}WebUntis/api/rest/extern/v1/students/{{id}}
and the OneRoster WebUntis API endpoints (with two different sets of credentials (for the iServ/Moodle integration in the section platform))

I'm trying to make an API call to this endpoint
GET {{EAP_URL}}WebUntis/api/rest/extern/v1/timetable
But I'm getting Error 403 "Access is denied".

Can any of you guys tell me how to make that call work?
Do I need to set up a different set of credentials with the the correct permissions? (if yes, how?)

Or is there a different endpoint that I can call to get the data needed?

Thank you!