If your Employment Authorization card is expired and the 90 days past from the received date on your "notice of action" you need to go to
www.uscis.gov and click on infopass, what they do is they will give you an appointment with an uscis officer at their closest office from you and they usually give you an appointment within a week, after that, you will receive you EAD card in the next 10 working days, and is OK to continue working because the will give you the new card with the expiration date from the last one extended to another year. SO DON"T QUIT YOUR JOB!
GOOD LUCK!