I don't know why. All I know is you have to use the Online Premier version to import it. Then you can move your return to the Desktop program without paying for the Online version.
You can call them and ask. How to contact Turbo Tax
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-contact-turbotax/00/26991
What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632
