[Quickie]

either you dont have the directory ".../scriptfiles/C4"

or this syntax

pawn Код:

format( string, sizeof ( string ), "/C4/%s.ini", user_name ); 
//change it to
    format( string, sizeof ( string ), "C4\%s.ini", user_name ); or     format( string, sizeof ( string ), "\C4\%s.ini", user_name );