I received this error for a number of real estate LLCs. In my case the solution was to open the K-1 Form and navigate to Section D1 on Page 6, which is where the Statement A information is entered, and manually enter the reported "Rental income (loss)" from my K-1 Statement A section.
Aspirin756 nailed it with this answer. TTX isn't picking up the info unless you do the above steps!!!
