to get a fresh latest copy of assignment.
Click File ==>Open
select all file except the assignment file and then delete.
Next select the assignment file and rename it, so the updated version gets download.
If you do not want to save the old copy, you can delete the assignment file too. In case you deleted the assignment file too, you get a 404 error in your screen.
if you don’t delete and rename the file, you do not get 404 error.
At this time, click 
on the right top corner, and then click reboot.
Once rebooting is done, click again, now click Get the latest Version and then Update Lab.
You have the latest copy of assignment to workup on.
Regards
DP