SOAP API - fetching Report Definition returning errors

Summary

Getting issues trying to pull a report definition - can someone help me figure out what's wrong with my code? The error I get is 'An ID or LookupName must be provided'

Version

Oracle Service Cloud 18C

Code Snippet

        public void getAnalyticsReport(int reportId, RightNowSyncPortClient client)
        {
            Console.WriteLine("fetching report " + reportId.ToString());
            //Create new AnalyticsReport Object
            AnalyticsReport analyticsReport = new AnalyticsReport();
            //Specify a report ID of Public Reports>Common>Data integration>Opportunities
            ID