Can anyone help with this issue? I never had this problem before, but since my PC lost all data on all drives for reasons unknown. My multi player screen is half gone and cannot tune second player first image below. Game does see second guitar, and you see the graph move as if you were playing when multiplayer is clicked see below first image. Both guitars are seen but when asked to tune players 1&2 bottom guitar is half gone and cannot tune. Please help Thank You!!!

So I figured it out, and thanks if anyone tried to look for a solution. In options it had Non-exclusive windows full screen selected. It should be exclusive full screen selected. This is a great site with great people! Thanks!

I was having the same problem. Thanks for updating your post. Works fine now.