The Secretary shall respond in writing in no more than 60 days to matters raised in complaints of a substantial or serious nature that a State has failed to use funds in accordance with the provisions of this subchapter or the assurances provided by the State under
section 8624 of this title. For purposes of this paragraph, a violation of any one of the assurances contained in
section 8624(b) of this title that constitutes a disregard of such assurance shall be considered a serious complaint.