X15coin.conf not X15C.conf
Yes, your conf file name incorrect , should be X15coin.conf , please update the name ,thanks .
which folder have to put this config file?tnx
AppData folder. I find the easiest way to do this is to press the Windows key, and then search for %Appdata% without the quotes.
The search should return a folder called Roaming, click on there and look for the X15COIN folder.
This is the folder where you need to place the config file