Help! Assignments in Khan Academy / Disconnect with link in Google Classroom

I assigned assignments in Khan Academy and I posted the assignment in our Google Classroom. For some students, it shows the assignment completed in the score report. For other students, it shows they have done nothing on that same assigned activity. However, if I look under student activity, I can see that same activity done in Khan Academy, but it did not link that activity assignment in Khan Academy. This makes it very difficult to see the scores of the students on the assignments, as the scores section indicate that the assignment was not completed by the student. What is going on? Why would it allow them to do the assigned work in Khan but record it as activity and not post it to the assignment?

I really need the ability to go to the score section and see the scores of all of the assigned work on that report not having it record as separate activity on the student's account. When I look at student activity, it not only shows activity for my class, but activity for all of their classes.