I had a net business loss last year, and paid $989 in estimated taxes for 2018. Why is my refund $0?

Did you input your estimated tax payment into TurboTax?

I didn't enter it again, but it was already in Turbo Tax because I paid it via TT last year.

Looks like it doesn't carry forward, so I'll need to add it in. Thank you!

TurboTax doesn't automatically carry forward in case the payment isn't made.  In addition, the date of the estimated tax payment must be entered.

Please follow these instructions to enter your Estimated Taxes Paid:

• Login to your TurboTax Account
• Click "Take Me To My Return"
• Click "Search" in the upper right corner, then type "Estimates Paid" in the Search Box.  
• When the results populate, click the "Jump to Link" 
• From here you can enter any Federal, State, or Local Estimated Tax Payments you made during the year