I filed for an extension through the website a week ago, but have not yet received a confirmation that my request was accepted.

You can go to the following TurboTax website for the status of the e-filed extension at no charge.  If the extension was received and accepted, there will be date/time stamps for when it was received and for when it was accepted.  

https://turbotax.intuit.com/tax-tools/efile-status-lookup/

Thank you. I did not know that page existed.

You are welcome