There isn't anything you can do - you just have to wait until things change again. They usually do, although I have two members on another forum whose notification emails have been blocked for years - others have come and gone, as on here, but for these two there seems to be nothing anyone can do.
In an ideal world you would be able to contact the email provider and say that the emails aren't getting through and should be, but in practice there is nobody there who cares.
@Bodgeitandscarper You seem to think that there's some sort of conspiracy going on...?