Hello there, @VuyoAdams ...
Are you using an up-to-date web browser? Generally speaking, using either Mozilla Firefox or Google Chrome will be your best options here as you navigate around the Canvas website. And, if you are already using one of these browsers, have you tried switching to the other one to see if you have better luck submitting your assignment? You might also try clearing your browser history/cache to see if that helps:
I would also recommend that you reach out directly to your instructor...to let him/her know that you are having difficulties submitting the file. If none of these option work, then you might also try reaching out to Canvas Support. Contacting your instructor and Support are both covered in this document: How do I contact Canvas Support? - Canvas Community.
I hope these resources will be of help to you. Sing out if you have any other questions about this...thanks! Take care...be well.