An unexpected error occurred. Please try again later in “Survival Estimates that Vary with Time” Notebook submission
hi @Tahir_Yamin
welcome to the community 
this unexpected error during submission is usually a temporary issue with the coursera platform servers and not a problem with your code logic
i see you can try a few simple steps to fix this
first you can try to clear your browser cache or open the course in an incognito window and submit again sometimes it works
second make sure that your notebook file size is not too large , fix it by deleting any extra print statements or long error outputs you added , then save the file and try submitting
if it still fails you can go to the lab menu click reboot server or refresh workspace to get a fresh connection to the grader
let us know if it works after trying these steps
can you post screenshot of submission grader which provides info for each exercise why it failed.
Also confirm, in the notebook if you passed all the test.
Remember doing any editing, deleting outside markers such as ###Start and end code here###, can also lead to failed submission.
You haven’t provided much information on what measures you took to resolve this issue.