Problem with the headphones

When I connect my headphones to my U-Mix Control Pro I hear the music in both headphones and speakers without different, also when I push the Cue Button. The instruction says that I have to select "Mix Vibes ASIO U-Mix Control Pro" from the pull down menu but when I do this it tells me that there is an error: the peripheral is running in another process and to close it. Please, help me. I don't know how to solve this issue.
Thank you
Thank you