From the ACHP:

On April 3, 2020, the Advisory Council on Historic Preservation issued a blanket extension regarding the review under 36 CFR 800.12 of undertakings responding to COVID-19 emergency and disaster declarations. Three extensions were issued, the third of which was set to expire on December 31, 2020. Considering the likelihood of such declarations remaining in place into the foreseeable near future, and the ongoing need for federal agency responses to them, that extension is now set to expire on March 31, 2021.

The press release is also on the ACHP website.