For a long time the lowest keys on my keyboard don't give any sound (C-G). The lights are on and with every VST instrument I encounter the same problem. I don't have a split keyboard on. What could I do wrong? How to solve this? I am not a technician or very much in all the detailed specifics. I can of course use the rest of the keyboard without any problemen but it is still annoying that I can't use the whole range. Some help or direction would be appreciated.