First, understand that after 5 rejections the IRS will permanently disable your ability to file your 2020 tax return. At that point, you have no choice but to print, sign and mail it to the IRS. So at this point, we know you have at least 1 rejection from the IRS. Now the possible reasons for rejection.
1. The 2019 AGI you entered in TurboTax 2020 does not agree with the 2019 AGI the IRS has in their computers, or the IRS has not yet processed your 2019 tax return through their computers. If you know without a doubt the AGI is correct, then work back through the FILE tab and tell the program that you did not file a 2019 tax return. Then try again. If it gets accepted, then that pretty much confirms the IRS has not yet processed your 2019 tax return through their comptuers. (This was exactly the case when I was trying to e-file my mother-in-law's return)
2. You amended your 2019 tax return. If you used your AGI changed after the amendment was done, try using the AGI of your 2019 tax return before the amendment. It's possible the IRS has not processed the amended 2019 tax return yet - or if they did they haven't updated their computers with the changed AGI.
3. One thing that happens, and it's not all that common, is that you may have entered the 2019 AGI wrong by doing something as simple as transposing digits, or entering a decimal point where there should have been a comma.
4. If filing a joint return, make sure you have both tax filers entered in the return in the same order as they were in the 2019 return, and that you did not switch the PIN numbers. (also, if IP PINs are required, ensure you entered the correct IP PIN for each tax filer, and didn't swap those numbers either.)
5. You have already had 5 rejections. If so, the IRS computers have locked out your ability to e-file the 2020 tax return permanently. There is nothing you or anyone else can do to change that. So at this point you have absolutely no choice but to print, sign, date, and mail the tax return to the IRS. If you mail the returns, ensure you use a tracking service (such as certified mail) so that if the need arises you can prove not only that you mailed it, but that the IRS received it too.
