Why no soud in Sonic Frontiers Line 2 SE preamp

I have Sonic Frontiers Line 2 SE preamp. Every function is working, but no output sound. Badly need advice for direction. Tubes are fine, Mute function works fine, Standby function works. I do not use remote control. When I turn on the line 2, there two red lights on main board. I contacted Part Connection and thy suggested new matched tube set. I borrowed new set and it still did not make output sound. Please help me.