Apple is aware of an issue the prevents video playback from some .MP4 files. To fix this use the video converter linked in the "Fix Video Issues" section.
Video Recorder is a free online webcam recorder that requires no sign up. The only caveat is you must use Google Chrome web browser.
Google Meet can be used in most web browsers. Create a meeting and join it. Then at the bottom right hand side of the window click the 3 vertical dots and then select record at the top of that menu. Hangup/leave the meeting to stop the recording. The file will be automatically saved to your google drive.
QuickTime PLayer is a program already on all Apple devices and downloadable for Windows devices. Click on link to see how to record. (not for ChromeBooks)
Zoom can also be used to capture your video either through their downloadable app.
Schoology: If your school uses this, Schoology has a built in Video Recorder that students or you can use. The only problem is that it saves as a .webm file which will need to be converted before used in Final Cut Pro. This in not recommended because the file sizes are small (low quality)
Wireless Headphones can be used to record.
You cannot use them to create practice tracks due to BlueTooth lag.
Earbuds with a microphone will sound better than the built in microphone on the chromebooks. (be sure the mic on the earbuds is not touching your clothing or hair)
Google classroom users can directly link this form to your classroom assignment so that the student's work will be shown as "Turned In".
If the file is still black/blank after the conversion then it's most likely the student wanted to record the audio only and had their phone face down during the capture.