If you used the Desktop CD/Download program for 2018 you can not save or store your return in your online account at Turbo Tax. And Turbo Tax won't know you did a 2018 return. The pdf and .tax2018 files are only saved on your computer.
Are you using the 2019 Online version or Desktop program? Do you want to transfer 2018 into 2019? You can transfer a Desktop return into the Online version.
How to transfer into the Online version
https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...
How to transfer into Windows Desktop
https://ttlc.intuit.com/community/entering-importing/help/transfer-last-year-s-return-to-turbotax-fo...
How to transfer into Mac Desktop
https://ttlc.intuit.com/community/tax-data-file/help/how-do-i-transfer-last-year-s-return-into-the-t...
