What options do I have for filing 2017 taxes with turbo tax if I can't download the software?

You do not say why you cannot download the 2017 software.  You are posting your question from a computer using Windows 10.  The 2017 software does need to be downloaded to a full PC or Mac, not a mobile device.  If you cannot do that, then you could also prepare the return by hand on the paper forms.

2017

https://www.irs.gov/pub/irs-pdf/f1040.pdf

https://www.irs.gov/pub/irs-pdf/i1040gi.pdf

https://www.irs.gov/pub/irs-prior/f1040a--2017.pdf

https://www.irs.gov/pub/irs-prior/i1040a--2017.pdf

https://www.irs.gov/pub/irs-prior/f1040ez--2017.pdf

https://www.irs.gov/pub/irs-prior/i1040ez--2017.pdf

Remember state taxes as well.