Week 3 : Submission score - passed all tests but still failed

Please help how to resolve hidden errors problem. {Passed all tests but still failing: 63/100.

Error message mentioned below:

Error Message:

[ValidateApp | INFO] Validating
[ValidateApp | INFO] Executing notebook with kernel: python3
Tests failed on 3 cell(s)! These tests could be hidden. Please check
your submission.

Sorry that the grader doesn’t give more useful feedback in a case like this. Are you sure that you didn’t reference any global variables or hard-code any parameters in your nn_model function when you call the lower level functions?

Thanks, It is resolved now.
I rewrite the whole code and it worked fine