Below is a direct message from the U.S. Customs and Border Protection (CBP).
Due to planned maintenance, the Food and Drug Administration (FDA) Import Trade Auxiliary Communications System (ITACS) document upload and Notice download functionalities will be unavailable Friday, 11/20/2020 11:00pm – Saturday 11/21/2020 8:00am ET.
If documents must be submitted during that time, they can also be submitted to the local FDA office at the port of entry via that office’s preferred alternate communication method. Contact information for all FDA import offices can be found on FDA’s Import Offices and Ports of Entry web page.
Questions regarding the maintenance window can be sent to ITACS Support at ITACSSupport@fda.hhs.gov.
Source: U.S. Customs and Border Protection (CBP)