5500-EZ late filing

Plan sponsor files form 5500-EZ in October.  Plan sponsor thought an extension was filed, but IRS has sent Notice CP-220 assessing a penalty.  Can plan sponsor still use the IRS Penalty Relief Program and pay the $500?  Notice CP 283 has not been received, but the 5500-EZ was actually filed.  

@Just Tri - I am in the similar situation. Received a CP-220 notice with $150K penalty. Were you able to use the IRS Penalty Relief Program (& pay the $500) and resolve this ? Greatly appreciate your response

I had mailed the 5500-EZ on time, but IRS says then did not receive it and I dont have the documentation of prrof of my mailing ...