I just manually checked the API. All entries from 2020-11-08 through 2020-11-14 on the website are missing due to some arbitrary reason. 14th through 18th again has the JSON as expected (I stopped manually checking after 18th). It makes no sense.
TL;DR: https://epic.gsfc.nasa.gov/api/enhanced/date/2020-11-13, and many other date results, are an empty JSON.