why are you unable to e-file for an extension? do you get an error message.? if so and you tell us the reject message maybe we can help. other methods include printing and mailing in form 4868.
here's a link to the form. note that the due date in the instructions is wrong. it should be 7/15/2020.
https://www.irs.gov/pub/irs-pdf/f4868.pdf
you can use this link to get to the freefile website to e-file your extension only
https://www.freefilefillableforms.com/#/fd/EconomicImpactPayment
