Factoryboy build is showing object does not exist

Question

@pytest.mark.django_db(transaction=True)
class testAllAPIEndPoints(TestCase):

    # This function will help us authenticate as admin
    def authenticate_asAdmin(self):
        self.user = AdminFactory.create() 
        self.token = Token.objects.create(user= self.user)
        self.client.force_login(self.user)

    # This function will build an instructor. Note: build does not commit to database
    def build_instructor(self):
        user = UserFactory()
        inst = InstructorFactory.build(user=user)
        return inst

    def test_addCourses(self):
        self.authenticate_asAdmin()
        inst = self.build_instructor()    
        course = CourseFactory.build() # Creates a new course
        tag = self.build_courseTag()

        print("tag")
        print(tag.id)

        data = dict(
                        name=course.name,
                        description = course.description,
                        instructor = inst.user.id,
                        tags = [tag.id]
                    )
        
        # Error I am getting:
        # b'{"instructor":["Invalid pk \\"10795\\" - object does not exist."]}'

        response =self.client.post('http://localhost:8000/api/courses/', 
                                    data = data, 
                                    headers={'Content-Type': 'application/json','Authorization':'Token ' + self.token.key}, follow=True)
        print(response.content)
        self.assertEqual(response.status_code, status.HTTP_201_CREATED)

I am trying to add course here which has instructor as foreign key. I am using the build() function from factory boy which as I can see is working fine. I tried to create a create function instead like this:

# This function will create an instructor. Note: create will commit to database
    def create_instructor(self):
        inst = InstructorFactory.create()
        return inst

And then creating a new instructor:

inst = self.create_instructor()  

but I am getting similar error:

b'{"instructor":["Invalid pk \"11105\" - object does not exist."]}'