Unless you filed an extension (Form 7004), the return for your S corporation was due March 16th.
See https://www.irs.gov/instructions/i1120s#idm139641016916032
Unlike returns that were initially due on April 15th and extended due to the pandemic, the due date for returns due prior to April 15th (e.g., Forms 1120-S and 1065) was not extended.
