CP162 notice and late filing penalty of $420 assessed on May 31, 2021 for 2020 form 1120S  but an extension was mailed March 10, 2021  Responded with letter asking for abatement on June 7th but no response from IRS. The IRS  sent CP5048 by certified mail and received July 2, 2021 threatening to seize property for non payment of penalty plus interest. Cannot reach IRS by phone number given. Should I send another letter to new address given? What alternative do I have?