This is at KMEM in PMDG 777F. Everything was fine yesterday, No changes or installs. Double checked Key assignments and Sft Ctrl F12 is not duplicated.
The "bong" sound clearly indicates GSX is working normally, and it's trying to tell you something (like turn on the parking brake or turn off the engines, or another error), but since you have disabled the information text, you cannot see what's GSX is trying to tell you.
Be sure you haven't mistakenly disabled the information text in the settings, otherwise no message from any application that use the top green bar will ever appear.