Hey @Subigya_Paudel,
It seems like your code has an error that is not being caught by both, the test-cases and the auto-grader, and as a result, even though your assignment is receiving a full score, you are unable to train the model. This is because, I ran the notebook myself in Coursera labs, and it is running perfectly fine. Can you please DM your notebook as an attachment to me? You can find the instructions to download your notebook here.
Cheers,
Elemento