Multiple Contextual Filters
It is because how you get them,contextual filter usually get from url and when you have 2 , you should have 2 parameter in url , as example  it should something like "mysite.com/3/reza",
this is one step, another step is that you  specified in your contextual filter that which arg is for this filter(put your default value in raw value form url,then you see path componet), (in my sample 3 is arg(0) and reza is arg(1) ) and if you  observe this note it work for you correctly.