I took my ATP written in 2003 and received a 737 type-rating and ATP on my initial qualification eval on the C-40 (B737NG). I have flown the C-40 since that time and remained current by USAF guidelines.
I assume that since I am not employed by a Part 121 carrier, it has expired. Does that check?
You have already obtained the certificate. The written is a prerequisite to the practical test. Once the practical test is complete you have your ATP certificate which never expires. You do not need to have a written test.