Can I get the 2nd stimulus check if my tax return got rejected last year?

Yes. Although the stimulus payment was sent out based on the 2019 (or 2018) tax return, it is reconciled on the 2020 return.

In TurboTax Online, to claim the Recovery Rebate credit please do the following:

1. Sign into your account and continue from where you left off
2. Click on Federal in the left-hand column, then on Federal Review on the top of the screen
3. On the next page titled Let's make sure you got the right stimulus amount, click on Continue
4. Follow the interview TurboTax will determine whether you are entitled to any additional stimulus
5. Any stimulus amount remaining due to you will show as a credit on line 30 of your form 1040.
6. See the image below for assistance.