the rejection is because 2018 can no longer be prepared or e-filed using online software. the online is for 2019 only. you would need to have a computer and then purchase the 2018 desktop software. 2018 return will have to be mailed in.
Do not try to file a 2018 return that you prepared incorrectly using the current online program. Online is only for 2019. If you have any 2019 income to enter on a 2019 return you can clear out the 2018 income and use the account for a 2019 return, or you can just abandon it.
Online preparation and e-filing for 2016, 2017 and 2018 is permanently closed.
To file a return for a prior tax year
If you need to prepare a return for 2016, 2017, or 2018 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.
Remember to prepare your state return as well—if you live in a state that has a state income tax.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Note: The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac. It cannot be used on a mobile device.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.