Does anyone know how to fix this?

Ok, so my Thunderbird updated this week to a new version, which I don't like very much but that's besides the point. Anyway, I always leave Thunderbird open (24/7) and I have a notification sound to let me know when mail comes in that I have been using for well over a decade now, but as of this last update my Thunderbird no longer plays that sound at all. I have tried every fix I could find online (ie: checking if its muted in volume mixer, making sure the default/proper sound source is selected, changing the drive for the custom notification sound, you name it I tried it) and NOTHING works. Even trying to use just the basic default notification sound doesn't work at all anymore. I have even gone to the length of completely reinstall Thunderbird itself but the problem persists. When I click PLAY in the settings it plays the sound just fine, any sound I select, so I KNOW the sound is perfectly fine...it's Thunderbird itself that seems to be broken. It just will not play ANY notification sounds all of a sudden. I need an email client open, and I absolutely NEED the notification sound. I have been using Thunderbird for like 15 yrs, I really really don't want to have to switch to a new client over something like this, but like I said I NEED that notification sound and if I can't get it working again I'll have no choice. can anyone help PLEASE?!?! I'm desperate!