What should we do when 2018 was filed before 2019 yet the IRS said it's wrong. We used Turbo Tax for this year. Still have to file 2018 and 2019 fast.

Oh, you are so lucky that wrong 2018 return was rejected.  The online software program is ONLY for 2019--no other year. That rejection just saved you months of amending an incorrect return.

Now---clear out the 2018 income you entered into that return.  NOTHING from 2019 belongs on that return.  Put only 2019 information in there.  When you try to e-file, use "zero" for the AGI.  If zero will not let you e-file, then print, sign and mail the return.

As for how to prepare and file your 2018 return the correct way:

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)

https://turbotax.intuit.com/personal-taxes/past-years-products/

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.