I am trying to fill out for financial aid, and in doing so I need to have a copy of my 2017 1040 form. My account already says it is plus but I can't access 2017 still.

You have to pay for the Plus edition before you will have access to the prior year online tax returns.

To pay the TurboTax online account fees by credit card so you can access your prior year online tax returns, click on Tax Tools on the left side of the online program screen.  Then click on Print Center.  Then click on Print, save or preview this year's return.  On the next page, to pay by credit card, click Pay Now.  On the next screen just click on the Continue button.  The next screen will show a review of your Fees, click on Continue.  Complete the next screen to pay by credit card and click Continue.

When I access the print center and click on the following option to preview the previous year's return I do not get another page that allows me to pay via credit card. After clicking on that option I am then taken back to the turbotax home page for my 2018 return. I don't know if I am supposed to get another webpage or what?

Then click on Print, save or preview  THIS  year's return.   NOT LAST year's return.

You clicked on the wrong link.  You clicked on "Print or view a prior year return" instead of "Print, save or preview this year's return"