App Doesn't Show Up on Sound Mixer

I'm about to give up on this after spending several hours un/reinstalling audio driver.
I even tried reinstalling my Windows 10 X64 Version 1909 (Os Build 18363.592) but to no avail.
I've updated my drivers using Snappy Drivers
I enabled/disabled "Allow Applications to Take Exclusive Control of This Device". It didn't solve the problem.

The app is TC2000. It's a charting software for stocks. I contacted their support and they don't know the solution either.
It has alert notification which gives you an audible alert when the criteria you've set has met in the market.
It works flawlessly in Windows 7 but not in Windows 10.

Other apps (games, browsers, etc) have no problem showing up in the "Volume Mixer" when right-clicking on the audio icon in the tool bar.

I've tried everything I could and I'm reaching out for help.

Perhaps it is something like this problem.

Desktop Application Notification sound not working - Trouble Shooting - Mattermost, Inc.

It doesn't seem to solve my problem. But thank you.

How are you running the app since it works OK in Win 7? Is it installed in a Win 7 compatibility mode? or native Win 10? If its an old app has it been updated for Win 10? if not run it in a Win 7 compatibility mode and see if that helps.

Keep in mind that when everything works as expected except one app, its the app and not the PC or OS software that is the issue.