My bad! You have to set a title for a message, so change this:
PHP Code:
$pm->setmessage("You won the raffle! Congratulations! {$pool} CURRENCY has been added to your account.");
To this:
PHP Code:
$pm->setmessage("Raffle prize", "You won the raffle! Congratulations! {$pool} CURRENCY has been added to your account.");
It should work now.