Hello Joshua @Joshua_Neft,
Please follow these steps to get a fresh copy of the assignment, and then you may copy your work from your current notebook to the fresh one.
Please read this coursera post about resetting deadlines. However, the deadlines are only for your own reference, and does not affect your grade nor certificate. You may just finish any overdue quizzes or assignments now without resetting deadlines, and you can receive full marks as long as all questions/exercises are correct.
Cheers,
Raymond