My daughter filed as my dependent in 2019. In 2020 she files single ($27,000). She has not been able to receive a stimulus check, how can she

When she files her 2020 return and if she cannot be your dependent she will get the stimulus based on that return.  If she CAN be your dependent—even though you don’t claim her—she must indicate that on her return. In that case she would not get the stimulus payment. 

If she does not meet the criteria to be claimed as a dependent for 2020 then she can receive the stimulus money when she prepares and files her 2020 return.  It would be best for her to wait until late February so that there will be no confusion about the second stimulus.

The stimulus check is an advance on a credit you can receive on your 2020 tax return.  If something went wrong or you did not get the stimulus check this year, you can get it when you file your 2020 return in early 2021—if you are eligible.It will end up on line 30 of your 2020 Form 1040.

https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-j-reconciling-on-your-2020-tax-return

https://www.irs.gov/coronavirus/coronavirus-tax-relief-and-economic-impact-payments-for-individuals-and-families

https://ttlc.intuit.com/community/tax-topics/help/how-will-the-stimulus-package-impact-me/00/1393859