I'm stuck at the first challenge where it always returns me:
Could not find an entry in the ServiceCredentials custom setting named 'BillingServiceCredential' with the specified username and password. Ensure the you have entered the data correctly into the custom settings record.
I think that I did everything right. The unmanaged package came with a custom setting called ServiceCredentials:
I clicked manage and added the BillingServiceCredential
With following details
Still giving me above error!