New WD External Drive Can't Eject & Files Won't Display on MacOS
Restart your Mac

At the risk of stating the obvious (as you didn't say you've tried this), have you fully shutdown your Mac and then rebooted to see if the drive appears and functions okay then? 

Use a different port

Shutdown your Mac and try connecting the drive to another port. What happens?

Safe Mode

If restarting your Mac and trying a different port makes no difference, can you restart your Mac in Safe Mode and let us know how that goes?

Follow these steps boot your Mac into Safe Mode:


Fully shut down your Mac
Restart your Mac
Immediately press the Shift key and keep it down 
Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
Take a note of what happens (i.e. could you boot your Mac okay, is the issue still present, etc)
To exit Safe Mode just restart your Mac as normal


Once you've booted into Safe Mode, let me know how you went and we'll go from there.

BACKUP

Finally, you really should have a backup of your data. You've made it pretty clear you have valuable footage on this drive you can't risk losing, so you really should have a second drive for backup purposes.