It’s not unusual for people representing themselves before the US Patent and Trademark Office to unintentionally miss a deadline. In many cases you can petition to revive your application.
For a small or micro entity, you need to submit an $850 fee for the petition to revive, a complete reply to the last mailing from the Patent and Trademark Office, a statement that the abandonment was unintentional, and, if necessary, a terminal disclaimer – a statement saying that you will take some time off the life of the patent because of your delay.
If you believe you have missed a deadline, it’s important to act quickly, extended delays may make it difficult to revive the application. In some cases, a poor record with regard to how the application was abandoned may make it difficult to assert the patent in later litigation.