That depends on the date(s) of your payment, and the extent to which an overpayment exists as of April 15, 2021.
If you made payments on or before 4/15/21 in excess of your 2020 tax liability resulting in an overpayment on your 1040 return, you may apply it to any first quarter estimated taxes due. However, you cannot bump up the 5/17/21 extension to cover the 4/15/21 estimate taxes.
View the IRS explanation [here] along with examples.
Questions? Contact us at 401-831-0200.