Curious. I know there has been a problem with users accessing 2018 .tax files; I haven't heard of a problem with 2017.
Before I ask you to call TurboTax Support, I'll ask if you've begun a TurboTax Online return for 2020. Sometimes even beginning a current-year return (just personal info, basically), will unlock prior-year returns. I can't say if this will work, but it's worth a try.
One other thing: If you typically use the Free Edition of TurboTax, you may need to purchase the minimum paid product to access prior-year returns. But you'll see that hyperlink in the TurboTax article you cited in your question. Telephone Support, too, is not a feature of the Free Edition of TurboTax.
How do I contact TurboTax?
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
