This is mainly a user community forum, not a direct route to TurboTax Support. But we can help you with that and how to pay for PLUS with credit/debit card.
Is your 2015 return locked because it was prepared in Free Edition, and when you try to print/download/view, it asks you to upgrade to PLUS? If so, and if you have already upgraded to PLUS, then whatever you do, do NOT upgrade any further, or you'll have problems.
We can tell you the precise steps to upgrade and pay for PLUS (29.99) with credit/debit card. First I need to ask some questions:
How to upgrade and pay depends on what you have done for your current 2016 return. Have you already filed your 2016 return with Online TurboTax, or is it still in preparation? Was the 2016 return in Free Edition? Or was it prepared outside of TurboTax?
Is the locked 2015 return in the SAME account as the one you used/are using for the 2016 return?
I'll give you more info when you answer all the questions above.
Here's another option:
If you don't want to pay the 29.99 for PLUS, a free tax return transcript might serve your purpose. Many lenders, student financial aid offices, etc. may accept one. You'd have to check with them. You may be able to download a free 2015 return transcript at this IRS website:
<a rel="nofollow" target="_blank" href="
http://www.irs.gov/Individuals/Get-Transcript">http://www.irs.gov/Individuals/Get-Transcript</a>
Or if you just need the 2015 AGI, look in the 2015 Tax Timeline and go to "Some things you can do." See if there is a link for "View 2015 adjusted gross income (AGI.)" Or the transcript method will also have the 2015 AGI.
