You will have to use your user ID and password you originally used for your 2018 TurboTax account. 

If you do not have your user ID and or password this link Forgot your TurboTax Online User ID or password? has information on recovering your account.

I have done my 2019 tax under my sister's log in because I needed Deluxe this year. Now it won't let me go back to my original log in. I need my 2018 because I can't find my printed copy and need my AGI. It was done on someone else computer who I cannot reach

@jvaladez08 If you do not have access to TurboTax for last year because you used someone else's account and you need your AGI you can obtain that information from the IRS by ordering a tax transcript. Please see this TurboTax FAQ for more information: https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/00/25947

Thank you Jeanne. After much fishing about, I was finally able to access her account after a few lock outs. Mission accomplished, got a copy of the return downloaded and printed. Have the right AGI and resubmitted. Don't think I could tell someone else how to do it other than to be persistent! 🙂

To check the status of you returns to make sure that they are not rejected again please click the following link: https://ttlc.intuit.com/community/rejections/help/how-do-i-fix-a-rejected-return/00/26136