Tryping to convert with this tool:
and getting this error, how to fix it?
See the Units and Symbol Size page for more information. The problem is that you actually have to set your symbol sizes in metres, feet etc, and not points. This does mean that the point symbology will be at a fixed size and not change when you zoom in and out.
If you check the symbology now, the symbols size should be in metres, feet etc. and the Layer 3D to Featureclass tool should now work. See attached screenshot.
Same instructions as above for polylines. Change that setting in the properties of your polyline layer and make sure your line width in the symbology is showing metres\feet etc.
That should remove the error in the tool.
I got this error when creating Realistic Trees. I can't check the setting in properties that you suggested, and I can't effect the symbology since it's the software that handles that. Do you have any suggestions in this specific case?