You tried plotting a Road long section and you got an error when you clicked on Selected Sections.

If you have a look at the Selected Sections list, make sure that NOT ALL sections are turned OFF for plotting on the long section - if no sections are selected for plotting then this will cause an error.

It will also cause an error when plotting cross sections or doing setout.

To fix this, click on Selected Sections in the Roads Ribbon Tab, Plan Production Panel and tick on what to include in Long Section plotting outputs.