once I pressed for longer time the Mute button, the sound came out. Love it.
Glad you're back on track!
PS: Should I update the 990 software using USB connection?????
The latest firmware version is v3.24, released in May 2008. I cover firmware updates
here, including how to install, how to see what version you have, and what the updates changed. I'd definitely want to at least run v3.11 (which you probably already are).