Hello, I built a test class and ran it receiving this error message: Required_Field_Missing on line 41 Column 1. GW_Volunteers__Volunter_Job__c

I created a new volunteer job, retrieved the Id of the volunteer job, and set the volunteer job field to the id when creating a new Volunteer Shift. I highlighted the sections in bold.

@isTest
public class createSoulAttendanceTest {

    public static String CRON_EXP = '0 0 0 3 7 ? 2019';
    static testmethod void testScheduledJob() {
        
        //Create Contact
        Contact con = new Contact(Lastname = 'Brown');
        
        insert con;
        
        //Grab contact Id
        Id conId = con.Id;
        
        //Create Campaign
        Campaign soulCam = new Campaign(Name = 'Soul Studio');
        
        insert soulCam;
        
        //Grab Campaign Id
        Id camId = soulCam.Id;
        
        //Create Volunteer Job
        GW_Volunteers__Volunteer_Job__c job = new GW_Volunteers__Volunteer_Job__c(GW_Volunteers__Campaign__c = camID, Name = 'Monday');
        //Grab Volunteer Job ID
        Id jobId = job.Id;
        
        //Set Date/Time for Volunteer Shifts
        DateTime dt = DateTime.now(); 
        
        //Create list to hold all the shifts
        List<Id> allShiftList = new List<Id>();
        
        //Create 7 Volunteer Shifts
        for(Integer i = 0; i < 6; i++) {
            GW_Volunteers__Volunteer_Shift__c shift = new GW_Volunteers__Volunteer_Shift__c(Program__c = camID,                 GW_Volunteers__Volunteer_Job__c = jobId,                                         GW_Volunteers__Start_Date_Time__c = dt.addDays(i),                                                               GW_Volunteers__Duration__c = 5);
            insert shift;
            
            allShiftList.add(shift.Id);
            
        }
        
        //Create New Program Enrollment
        Program_Enrollment__c proEnroll = new Program_Enrollment__c(Campaign__c = camId,
                                                                   Attendee__c = conId,
                                                                   Volunteer_Job__c = jobId,
                                                                   Status__c = 'Confirmed',
                                                                   Role__c = 'Participant',
                                                                   For_All_Sessions__c = FALSE);
        //Retrieve Program Enrollment Id
        Id proId = proEnroll.Id;
        
       Test.startTest();
       String apexJobId = System.schedule('ScheduleApexTest', CRON_EXP, new createSoulAttendance());
       Test.stopTest();
        
       List<Attendance__c> att = [SELECT Id FROM Attendance__c
                                 WHERE Program_Enrollment__c =: proId
                                 AND Date__c >= TODAY 
                                 AND Date__c = NEXT_n_DAYS:7];
        
       System.assertEquals(allShiftList.size(), att.size());
    }
}

Any help in why this error is happening is greatly appreciated!