Error - 1. Insufficient points for triangulation. You need at least 3

[Daniele7 (Daniele)]

I am trying to transform the 3D curves (exported from QGIS) into terrain, as I have always done, with the procedure of which I attach the screen. But when selecting set multiplies curves, I get the following error message: 1. Insufficient points for triangulation. You need at least 3.
It has never happened to me and I have always transformed the curves into terrai

n with this method, without any problem.
I hope you can help me

[martinsiegrist]

This looks like one of your curves is a line with just a start and end point.