well… you have this “problem” because you use your own rebar bars. If you would have been using the ones that we deliver with our rebar families you would not have this issue.
From “other” drop-down menu you have “content folder” which will lead you to the folder with the rebar families that we deliver with the installation and a revit template file
There is no big issue if this warning comes up. We have build it to make the user aware that he didn’t filled up the mass per length parameter that we have. If this is not filled I think you already observed that the weight in schedule is not 0 and the rebars have a hard coded value for mass per length.
I hope I could make the situation a bit more clear now.
Enjoy Reinforcement Detailing!