I test it every so often, but in tha past month I haven't recieved any coins from it
I may happen for many reasons. Write Bitcoin address that you have used to request prizes, I will check.
How to place an ad? Because I click on "Place new add" button and nothing happens...
This button uses JavaScript, therefore it must be enabled in your browser and script not blocked by some extension like AdBlock.
BTW, what browser do you use?