Hello Skagoose,
Be sure to check and see if the volume issue is affecting multiple apps, to see if it's specific to a particular one. Checking to see if the system's volume slider and the video's volume slider are both adjusted as desired can help too.
This page can help provide steps for this type of issue as well: If the internal speakers on your Mac aren't working - Apple Support
Check your sound settings
First, disconnect any cables from the USB, Thunderbolt, or 3.5mm audio ports on your Mac.
1. From the Apple menu , choose System Settings (or System Preferences).
2. Click Sound.
3. Click the Output tab, then select the built-in speakers. If you don’t see built-in speakers as an option in the Output window, contact Apple Support.
4. If the Output volume slider is set low, move the slider to the right and test again.
5. If the Mute checkbox is selected, deselect it and test again.
6. If you still don’t hear any sound, contact Apple Support.
Checking the issue out within a newly created Admin account on the Mac can help to rule out other apps or login items from affecting things, and see if it's a system-wide issue. This page can help set up the other account if needed: Add a user or group on Mac - Apple Support
Cheers.