I'm not sure here is the right place to report, but this issue is related to specific to A-10C II cockpit .edm file in the following directory:
\Mods\aircraft\A-10C_2\Cockpit\Shape\A-10C-2020-CPT.EDM
As described in the title, the "Generate livery file" option is inop. only when Hawg 2 cockpit model is loaded, it functions well on other model files.
For your information the Modelviewer i'm using is the stock one in \bin folder.