Purchased 2017 TurboTax Online to prepare tax returns. Filed an extension, but cannot re-access online file to finish tax returns - albeit past due date. How do I access?

You can no longer prepare a 2017 return online, which is now only for 2018 returns.  So here's how to proceed:

You can use 2017 desktop software to finish.  You can download the *.tax2017 data file you started, and since you already paid, you can contact TurboTax Support to ask for the desktop software to install.   If you don't reach them in the next 17 minutes, then you won't be able to speak to them until Wednesday, January 2.

If you are having trouble getting your *.tax2017 data file you started, report back and describe the roadblock.

Your 2017 return will have to be printed, signed, and mailed.  It cannot be efiled at this point in time.

FAQ:  What is the TurboTax phone number?

https://ttlc.intuit.com/replies/3300041

NOTE:   If you used Self-Employed Edition online,  be aware that the desktop software is called Home and Business Edition.

Also if your *.tax2017 data file has a state return started in it, then you will need to download the state program into your desktop software before it will open the *.tax2017 data file.   Otherwise you will get an error notice.