Filing extension - Transmit my return button not doing anything

[SusanY1]

Try clearing browser cache and cookies (in your browser settings) and then trying again.  This will often resolve the issue. 

[fanfare]

You don’t need to file Form 4868 if you make a payment using the IRS
electronic payment options. 
You can pay all or part of your estimated income tax due and **indicate that the payment is for an extension** using Direct Pay, the Electronic Federal Tax Payment System, or using a credit or debit card. Your extension is then automatically granted and you will receive a confirmation number for your records.

I hope you're on the West Coast.