They requested pre-interview a valid First Class Medical with First Class privledges. The way I interpreted the reg was since I don't have an ATP and I am not interviewing for a job that requires the ATP my 9 month old First Class was still valid.
Your First Class is still valid (which meets the first part of their request which is valid First Class Medical). After 6 calendar months from issue though it will only allow for privileges of 2nd class (so you failed the second part of their request with First Class privledges which is why I guess you got bounced).