I am in the same boat. My 18 month extension expires March 18. I called and asked for infopass and spoke to someone that said they sent me an extension in November. While if so it never arrived? She said she would ask for it to be resent but it could take a month??? Carrier pigeon i guess? Anyways I have my n400 interview March 29 so I guess I will have to Uber there but while I am there something will hopefully get figured out.