Your ex-wife needs to file an answer (response) to your petition for divorce with the court and serve a copy on you by mail.  Both the filing with the court and serving a copy by mail on you must occur before the twenty day deadline for a response expires.  If she doesn't file her answer (response) to the petition and serve it on you within the twenty day period from the date she was served, you can request that a default judgment be filed with the court.  A default judgment means that your ex-wife has lost in terms of challenging your petition for divorce.  However, she can still file a motion to set aside the default.  If the court grants her motion to set aside the default, the case will then be back on track and litigation will continue.