It was a final return of the partnership and I showed the end of the year as November 18, 2020.
I have filed an extension for the partnership March 10 by certified mail and was sure that everything is fine. Shortly, after filing the extension on  March 19, 2021 I have filed the return. 
IRS issued a notice for penalty of $840 stating that the return is 2 months late (partnership 
had 2 partners). They say that I were suppose to file the extension  February 15, not March 15,
due to the short year of the partnership.
Is there any way to argue with them about this penalty.
Thank you for any advice.

ac