Using TurboTax Standard 2021 download version. The error appears when TurboTax checks the T1135 form to see if it is suitable for NetFiling. The error message gives no clue as to the cause, so the application developers should fix this, since it’s easy to code for. The user can choose one of two checkboxes to use either the “Part A” or “Part B” method for reporting the data. I completed the data section consistent with using the “Part B” method, but (I assume that it was me) the “Part A” checkbox was selected. So the TurboTax error message was essentially complaining that there was no data specified in the “Part A” data section, which is where it was looking because that was the checkbox that was selected. Selecting the “Part B” checkbox solved the problem.