Build from source packaging error (Megascan assets)

Hello,

I’m developing a VR experience using UE4 4.26 and I’m currently trying to add Multiplayer functionalities. To achieve that, I have downloaded UE4 4.26 from GitHub and built the Engine from source. I have then opened my existing project (everything went fine, no error). Now, I’m trying to package the game but the packaging fails because it can’t find some of the Megascans assets. How can I make sure that everything is imported to the project before packaging or how can I install Megascan in this built from source version to ensure all the required assets are present?

Thank you