I would definitely try to renew the CNA certification. Speak with your supervisor or the person in charge. Let them know that renewing your CNA certification is important to you and you would greatly appreciate it if they submit the extension form or any other necessary documentation. You must be polite and courteous. It is your responsibility to renew the certification in time. If there is anything your employer can do at this point to help you become recertified, then you should try to obtain it in a nice way. I am not familiar with the employer's responsibility in this case, and this is just my opinion regarding what you should do. This is not legal advice and should not be viewed as such.