Though i create the fields as follow, am getting the error at Data Integration Specialist SuperBadge Challenge#9

billAmount
BillDate
InvoicesId
OpportunityId
projectRef

Greetings, I've created my external object for the Data Integration Specalist Superbadge and have configured my external ID as seen below, however, the challenge seems to not pass, indicating that the indirect lookup was not properly created. Here's how I set up the projectRef__c field, which was what I used to push data from the external object into the project object in Salesforce. Are there any steps, I need to take. Hope it helps.