hi @tybenz25
To get a fresh copy,
Click file, then select open. You will find all the files related to the assignment. Here if you have saved a copy of your notebook with renaming other than what was mentioned. Then go ahead and delete the assignment notebook by selecting the particular notebook.
Once deleted, you will find 404 not found image on your browser. Then close the browser.
Open the assignment page again, when you open you will find 404 not found.
At this time, click 
on the right hand top corner Before Grades, where you will find Reboot. Click reboot.
Then click the same on the right hand top corner, then click Get latest version and then Update lab.
Only make sure this time when you write codes limit your codes between the markers mentioned in previous comment. I am not stating you might have, but sometimes when we try to run a cell, keyboard click here and there could lead to an editing which autograder might not allow and when we cannot find such minute error, this would be last resort.
Regards
DP