Do you find evidence of your past returns OK, but when you try to download, does it ask you to pay? If it was prepared in Free Edition last year, access will be locked. If that's your situation, we can tell you how to pay to unlock your past returns. The method to unlock them depends on what all you have done with your 2018 return.
If you found the prior returns, but access is locked, please answer all of the following:
We can tell you the precise steps to upgrade and pay to unlock them once you answer all the questions above.
There's also a free option if a return transcript will suit your purpose. You may be able to immediately download one at the IRS website if you qualify to open an IRS account there. Otherwise, to order a transcript to come by postal mail takes 5-10 calendar days.
They call that Plus benefits. You can add them after you have filed to get access to older filings.