I am not sure this has anything to do with gp but I am unable to add line numbers to code lines by using below tags.
I know by default there is no line numbering with above code but I have tried almost every syntax highlighter plugin without a success. Interestingly nothing happens. When I try basic themes they work but now with gp (I am using child theme).
I didnt say pre and code tags are not working. I am saying, I am not able to add LINE NUMBERS to my codes with any plugin I tried. When I switch to tweenty theme, I am able to do this with below plugin (for example)