It is too late to file an extension. You just file as soon as you can. The late filing penalty is a % of the tax due; so there is no penalty for filing late if you are getting a refund. If you are still unable to file, you can make a payment of your best estimate to stop the penalty from accruing. Use voucher form 1040-V (not form 1040-ES) to make the payment*.
*When entering the payment in TurboTax, with your filing, enter it as a payment made with extension, not an estimated payment.
