Instead of using its own native server, Google Classroom transfers all of the data to Drive. So as soon as I ran into this issue, I immediately opened the Drive app and tried to retrieve the movie there. It turns out that I was effortlessly able to play the exact same movie in Drive that was giving Classroom problems. This therefore proved that the problem is with Classroom and not Drive.
In light of this, let's move on to the solution to the problem of Google Drive movies not playing in Google Classroom.
Launch the Google Drive app on your device to get started.
Next, log in using the same account that you use to access Google Classroom.
Navigate to the Classroom folder where the movie was placed and then go there.
You should have no problems playing this video if you try to view it right now.
You have thus resolved the problem with Google Drive movies not playing in Google Classroom.
You shouldn't have any issues putting this update into place as the Drive servers are operating without a hitch. Google hasn't yet made the official patch available, so that's that.
The best solutions to fix Google Classroom not working is by contacting Google Classroom Support.