IRS rejected my amended return

[ouisiek]

Earlier this year, the Health Insurance Marketplace sent me an amended tax form 1095-a for 2018 with a letter saying that I might need to amend my 2018 return to include the form.  I promptly adjusted my return to include the form and filed an amendment along with a check for the amount owed.  Today I received a letter from the IRS saying that my amended 2018 return cannot be processed because "the statute period for the assessment has expired" and they will be returning the amended return payment that I sent.  Now what should I do?

[Anonymous_]

I'll page @Mike9241