Q&A: What can I do if I have not received notices since filing N400?(6/15/11)
Question: I filed form N400 in 1992 and received an acknowledgement letter back. It has been over 20 years since I filed and have not received anymore notices. How can I go about getting any response?
Answer: It is most likely that the USCIS (formerly INS) has lost your file or your application was denied but you did not receive the notice. It is hard to imaging that the government still holds your case without making a decision. You should just refile a new application.
You may file a request to get your immigration file so you can see what happened in your case.