The IRS can look at your 2018 or 2019 return to issue a stimulus check.  If they do not have a 2018 return then you may be waiting for them to finish processing 2019 before they will be able to use it to issue your stimulus check.

If you used the non-filer site, you will not be able to e-file a 2019 return after using the non-filer site.

TurboTax has no control over your stimulus check, nor can TT track it for you or tell you when the IRS will issue it. Refer to the sites linked below:

You can call the IRS hotline at 1-800-919-9835 to get updates on your stimulus payment.  

https://www.irs.gov/coronavirus/economic-impact-payment-information-center#nonfilertool

https://www.irs.gov/coronavirus/get-my-payment-frequently-asked-questions

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

"In essence, the stimulus check acts as an advance of your 2020 income tax refund. This means when you prepare your 2020 income tax return, there will be a line to include the section 6428 credit. The credit on your 2020 return is subtracted by any amount received as a stimulus check in 2020. If the amount you received as a stimulus check is less than the credit you are due, the difference will be included as part of your 2020 refund. If you have been overpaid by receiving the stimulus check, however, you will not be required to return any excess amount".