Create Record test is working, but sends empty schema fields

After some trial and error I got my create record for my Rest-API working. It mentions that the Status: OK. However, after filling in the custom schema (which are the same as the fields in the backend) the test does not include the schema data with it. So in the backend I do get a new record, but with the “Activity” and “Description” fields empty. Is there something I’m missing?