Hi - I get the error message : 

Challenge not yet complete... here's what's wrong: 
There was an unexpected error in your org which is preventing this assessment check from completing: System.DmlException: Process failed. First exception on row 0; first error: REQUIRED_FIELD_MISSING, missing required field: [nextApproverIds]: [nextApproverIds]

When running through the challenge "Routing Records with Approvals".
I did a test on a couple of records and the approval process is working as per the requirements of the challenge.

Thank you