Tunes match

My I Phone 4s won't let Music match stay on. I go to settings and to music and turn it on but when i go back to the home page and then back to settings or music it is back off. I tried loging out but all I could find is a loig out and in in the app store so I did it. I had a similer problem with my pro and a log in and out fixed the problem. I can't find this in the phone I store on the phone