Are you a teaching assistant? Or instructor of record?
If you're a TA, whatever the instructor of record says goes.
If you're an instructor of record, you should create a system that mitigates these kinds of last minute requests:
use the LMS (looks like Canvas) and not email as a submission system
make it an small assignment to make sure student know how to upload to the LMS
Build in grace periods and late penalties (canvas allows this, either through rubric or auto percent subtraction)
Recognize that student do have emergencies once in a while. Build it into your class as a "lab redo" or something. (How many depends on you)
Think hard about how to create a system to handle student who request for extensions that goes beyond the semester (who to give and what's an end-date)