Week 2 Assignment showing 0%

I have got 0 in my assignment but I have passes all exercises. After submitting the assignment it shows in every exercise that
There was a problem compiling the code from your notebook. Details:
name ‘A_ref’ is not defined

This issue may have been fixed by a recent update to the course.
Or it could have been a problem in your code with use of global variables, or an obsolete copy of the assignment.