If a SMSF fails to lodge their annual return each financial year it may stop further super contributions being received. You would receive an error after submitting super contribution information to the Clearing House. See: Lodge SMSF annual returns | Australian Taxation Office
A workaround for this situation would be to setup a new membership with your default super fund and make contributions for the employee here. Due to the change in fund as an employer, you would then be entitled to the 20-day extension period. Payment deadlines for Payday Super | Australian Taxation Office