Hello- Which web browser are you using? I would clear your browser data, reboot and try again with the current browser you have been using.
If it doesn't work after these steps- I would try to use the latest approved version of Firefox.
An inconvenient workaround (just to get this assignment done) may be to record the video onto the computer or even using the phone and upload it instead of using the record feature. But ideally in the long term you'll want this issue resolved. I reiterate @RonCote's suggestions.
I agree with the suggestions from @RonCote. Here are a few links for you:
Also, Canvas works best using either Google Chrome or Mozilla Firefox. You can also visit this Guide which includes a tool to check if your browser meets the minimum browser requirements. What are the browser and computer requirements for Instructure products?
Hope this helps a bit. Sing out if you have any other questions. And, if none of the above works, give Canvas Support a call.