I have the answer, first of all LNew for your case or LDM for mine is showing in Blue, that it means it is not defined yet. So, you have to define it first. You can define it in either Mathematica or in the .fr file. After having done that, from evaluate quit local kernel, and then rerun all the commands. Hope this helps :)

I also have the same error- has anyone found an answer?

Thank you

I tried again I don't know if you can see it better. I am pretty new to mathematica but there seems to be no easy way of copying and pasting so I uploaded the picture ][1] Here is the input if the image still couldn't be uploaded: In Starting Feynman rule calculation. Expanding the Lagrangian... Collecting the different structures that enter the vertex GetFC::Head : Wrong Head in FC. Symbol $Abofrted