My 2019 return was delayed so I didn't get 2nd stimulus check. When I filed 2020 with TT, I answered no, I didn't get it, but saw nothing about credit. What happens now?

That was all there is to it.  Actually, if you said no to the second one then a minimum of $600 should be added to your refund.  I said minimum because it depends on your filing status and number of exemptions on your return.

If you are unsure whether the credit is in your refund, you can check  by going to the Black strip on the left side of the software then go into My Tools, then tools, view 1040, then view summary.  Scroll thru return to the page with the refund then you can see what is included in the refund.

What is a Recovery Rebate Credit? 

The Recovery Rebate Credit is a credit that was authorized by the Coronavirus Aid, Relief, and Economic Security (CARES) Act. So, if you were eligible for an Economic Impact payment, commonly referred to as a stimulus payment, but did not receive one or you received less than the full amount as an advanced payment in 2020 then you can claim the Recovery Rebate Credit on your 2020 tax return. 

Generally, the credit can increase your refund amount or lower the taxes you may owe. 

More details see link below:

What is The Recovery Rebate Credit