I have always used AGS with the option that it will send me notify to my email everytime when I receive private messages. Suddenly, it just stopped without any reasons. I tried to reset the option, re-typing my email, but no, I do not receive anything and there's nothing in spam box either to look for.
I've noticed this as well, although I've just taken to visiting the forums more often to check for replies.
If anything, the only result is that I'm more active ;)
Since I didn't get an answer:
http://www.adventuregamestudio.co.uk/forums/index.php?topic=45853.msg631207#msg631207
... I guess CJ still has not reported yet or no time for this :~(
Sorry, but it looks very unlikely this will be working any time soon. There are plans for late this year / early next year that should sort it out though. So please wait another month and a bit!