SharePoint REST API: Not able to get list through API

Question

I am trying to get a list through the use of the sharepoint API.

If I am logged in I can access the XML response through the following URL: https://{sitenumber}.sharepoint.com/sites/AI/_api/web/lists/GetByTitle('[ListTitle]')

When I use an API call with OAuth enabled I get a 404. So it sais it does not exist.
If I try to list out all the lists within the AI site it displays the default lists, but not the new list I created.

I've tried numerous things like checking whether the list is hidden or find it by the GUID but that does not work.

I also tried to find settings to open up the list for API calls but can't find any such setting.
Getting userdetails through the API delivers my own credentials so OAuth seems to be working.

What am I missing?