Forum E-mail system not working

I’ve got all my posts to this forum marked “notify when a reply is posted” but this doesn’t seem to be happening. For example on 13 April there were at least 9 replies to my posts, but I received no e-mail notifications. I have checked all the locations where spam e-mail gets collected, and as far as I can see there’s nothing there. Why is this not working?

Thanks - Rowan