If you are owed a refund, nobody cares when you file.
What you must do timely is pay. There is no extension to pay.
To be more precise, the penalty for late filing is a formula based on what you owe. If you owe $0, the penalty is $0. Sadly the penalty does not go into negative numbers, so they won't pay you if they owe you! So to that effect the 4868 as an extension is fairly superfluous. However, it is rather useful as a payment coupon since 4868 does not extend the deadline to pay.
After April 15, 2022, you forfeit a right to a refund.
So focus on sending a payment to the state timely! You don't need to file your state, just get 'em paid. Use your stare's version of a Form 4868 for a coupon.
Postmark in the mail is good enough. Post offices no longer stay open until midnight on tax day, you have to get it in by normal close-of-business.
P.S. The railroads, who know a thing or two about Standard Time having invented it, take the viewpoint that 12:00:00 is ambiguous and midnight trains are in fact carded for 12:01 am.
Also remember that efile is not filing. It is consensual electronic data interchange in lieu of filing. IRS will cheerfully withdraw its consent if they don't like something about your figures. They can't do that if you paper file, unless the filing is obviously frivolous or incomplete.