Another letter will get it graded/evaluated/whatever they call it again, however I think there is some kind of a timeframe to that (6-12 moths maybe?). The point being if 20 guys all sent the email over 20 consecutive days, its not going to be graded 20 times, and even if it was it would be graded the same anyway.

In your case it doesn't seem like that much time went by between the email and when you fixed the issues in your app, and you never got a "fix it" email anyway, right? That makes me think it might not have been graded/tiered yet. Then again it depends on what you "fixed" yourself and if the initial app would have triggered a "fix it" query in the first place.

Maybe wait at least 6 months since the first email and then get another internal to do the email specifically stating that your app has been fixed. That's probably what I'd do.