2015 is beyond the 3 year statute of limitations for amending for an refund which is why it is no longer supported. TurboTax only support the last 3 years.
If you did not save a hard copy or pdf then your best bet is to get a free transcript from the IRS.
You can also obtain a free transcript of past returns from the IRS:
https://www.irs.gov/individuals/get-transcript
You can also get an exact copy of past tax returns from the IRS by using form 4506 for a $50 fee per tax return.
https://www.irs.gov/forms-pubs/about-form-4506
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
