I am unable to turn on mobile data for certain apps that i have turned off for before

I hae turned off data usage for some apps in my mobile data settings , now when i try to turn it on i am unable to as it turns off by itself the moment i exit the settings app and go into the app which i turned on data for . I have tried resetting my network settings and also checked for restrictions and everything is fine but my data still does not turn on for certain apps after switching it on