If you don't want to wait and don't mind paying you can buy the full Mac program download for each year here,
https://turbotax.intuit.com/personal-taxes/past-years-products/2018
Have you downloaded your tax returns as .tax2017 and .tax2018 files? The amend instructions says how to
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27371
