Stirrup with dynamo

I tried to place the stirrups of different spacings with dynamo, I copied the knots but I do not know where the error is.

Is it a 3d view? To make it easier to help, you should show the complete graph and include the error messages. (hoover the yellow bubbles)

Los errores son

1: Warning: Null value cannot be cast to Double
2. Warning: Vector.ByTwoPoints operation failed.

I really do not understand much, what I did was copy the knots of a tutorial, but I get that error. The value of the code block

Then you should double check that you have connected the wires correctly.

Thanks I’ll try