How to use PromptPurchaseFinished?

I need to print when product is purchased; the problem is that the function does not even print.

~~~~~~~~~~~~~~~~~ MarketService.MarketService.PromptPurchaseFinished:connect(function(c, a, isPurchased) print(c,a,isPurchased) if isPurchased then table.insert(server.que,server.eventInst:InvokeClient(c,'get_id'))

    server.eventInst:InvokeClient(c,'clear_id')
    server.eventInst:InvokeClient(c,'change_desc','- Successful -')
else
    server.eventInst:InvokeClient(c,'change_desc','- ERROR -')
end

end)(function(c, a, isPurchased) print(c,a,isPurchased) if isPurchased then -- DO STUFF HERE else -- DO STUFF HERE end end) ~~~~~~~~~~~~~~~~