If PLUS and Deluxe are both grayed out, then you are already upgraded too far. You appear to be using Deluxe. If you try to pay now, it will charge you 59.99 for Deluxe, and possibly 44.99 for a state return. PLUS, in contrast, is 19.99.
What to do now depends on the situation with your 2018 return.
Have you already filed the 2018 return? If so, you won't be able to downgrade to get into PLUS. In that case, you can phone TurboTax Support, tell them you accidentally upgraded too far and ask them to unlock the 2017 return. It's possible they might not even charge you.
If you haven't filed the 2018 return, we can tell you how to clear and start over. Then you can begin a return in Free Edition and upgrade to PLUS for 19.99. We can tell you all the steps.
Also, the 2017 and 2018 returns must be in the same account. Do you see that the 2017 return PDF is in the same account as 2018?
We can tell you more about what to do when you answer the above questions about your 2018 return.
There is also a free option. You may be able to immediately download a 2017 return transcript at the IRS website at the link below. If you don't qualify to open a free IRS account there, you can order one to come by postal mail, which normally takes 5-10 calendar days.
http://www.irs.gov/Individuals/Get-Transcript
