Technically, expiration of the conditional green card is expiration of the conditional permanent residence status. This is a big problem for filing Form I-751, Petition to Remove Conditions on Residence, which normally should be submitted to the USCIS within the 90-days period before the card expires. In addition, the following things become difficult or downright impossible with an expired green card: traveling, getting a job, renewing your driver’s license, buying a home.
If your conditional green card has already expired and you failed to file Form I-751 before the expiration date, do not wait for immigration officials to contact you, consult an immigration attorney immediately. Under certain circumstances, there are lawful ways to regain your conditional permanent resident status. USCIS can excuse the late filing if you provide a written explanation proving that the delay was caused by extraordinary circumstances beyond your control and that the length of delay was justified. However, you should do your best to file I-751 petition before your conditional green card expires, it will prevent further complications.