Course 4 Week 3: Unet

After the assignments submitted several times(still got zero), although I corrected all in LAB, I made the clear output before submitting :
"1. P​ress Kernel → Restart & Clear Output
2. P​ress File → Save and Checkpoint "
Could anybody help me with that?

Did you follow all the instructions in Important Note on Submission to the AutoGrader section of the notebook?
It’s possible that the notebook metadata is missing / corrupt. So, backup your work and remove / rename the assignment file. Refresh the workspace, fill all code and try again. If you still fail, please click my name and message your notebook as an attachment.