STOP! Online is only for 2019.
To do a prior year return you have to buy the Desktop program here, https://turbotax.intuit.com/personal-taxes/past-years-products/2017 You will need a full Windows or Mac to install it on.
How to prepare a prior year return
Or If you have a simple return You can fill out the blank forms for free.
Here are some blank forms & instructions for 2017
2017 Tax Tables https://www.irs.gov/pub/irs-prior/i1040tt--2017.pdf
Publication 17 Tax Guide for 2017 https://www.irs.gov/pub/irs-prior/p17--2017.pdf
Don’t forget your state. And you will have to print and mail your returns. So be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.
Then do you need to do 2019? If you tried to use the Online version for 2018 of 2017 and entered info into the 2019 Online version you can try to clear and start over so you can use it for 2019.
Or you can leave this account and set up a new account to do 2019. How to start another return in the Online version