I have an Ovation Celebrity acoustic and it has muted notes on the G string around the 9th fret. It also has muted notes on the high E string around the 14th fret. The guitar needs new strings and I'm not sure if buying a certain gauge strings will fix my problem. By the way I also have no idea what gauge strings are on there now. If I need to adjust the truss rod I will I just don't know how much to turn it and what direction.
If you live close to a music store, take it there and ask them to show you how to set it up. I would suggest 11s or 12s, depending on what you want.