What do you mean "all" the emails? Ie, how many of these have you done? Have you done them all the same way? If I had opportunity to do this multiple times and was wondering about this, given that it's only 50 points, I think I'd try it without the prefix one time and with the prefix another time. That way it seems to me in two tries or so you'd know whether the prefix is the problem or not!

Who is sending you the emails, Topguest or Choice? If Topguest, there's the posisbilty that Topguest transfers to Choice only once a week, only once every two weeks, only twice a month, or even only once a month. How long have you waited? (Different pairs of partners transfer at different frequencies, so just because Topguest transfers often to other hotels doesn't necessarily mean they transfer just as often to Choice.)