I couldn't locate that label.
The error message is generated as it says by the 2D script. You need to fix that.
Regarding the slope designation, you downloaded an object without the capability to display as you wish. Either have someone amend it to display as you want, or find another.
There were a couple of roof accessories that did what you want posted here on architalk, you might see if one of them will work in current versions of AC.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"