Thanks for checking the setting and getting back to us Mecca1211, it's appreciated.
Since the setting was already enabled, we'd like for you to perform a couple of isolation steps that can help us pinpoint the issue.
How to use safe mode on your Mac - Apple Support -- Restart your Mac in safe mode and see if you hear the swoosh. Once you've determined if it does or not, restart your Mac normally to exit safe mode. If you heard the sound when sending an email in safe mode, see if the sound is audible now.
Please be aware: "When you start up in safe mode, your Mac prevents some software, such as startup items, from loading, and it performs a check of your startup disk. Your Mac may take longer to start up because of the check."
New user or group setup - Apple Support -- If it doesn't, or it stopped working after exiting safe mode, please create a new Administrator account using the steps provided just above. Once created, log out of your account and into the new one. You'll need to set up an email account in order to test. This will determine if the issue is isolated to your account or is system-wide.
Please let us know the results when you're able by replying to this post.
All the best.