[17:39:21] [Render thread/WARN]: Missing metadata in pack optional_data
[17:39:21] [Render thread/WARN]: Missing metadata in pack required_data
[17:39:21] [Render thread/WARN]: Missing metadata in pack optional_data
[17:39:21] [Render thread/WARN]: Missing metadata in pack required_data

I'd appreciate some extra information, for example your mod loader of choice and the game version you're using.
Especially as the 4 warning above are mainly pointing at an incorrect configuration and nothing that should prevent anything not to load.

I think it was just due to using the default location it was having issues, when I set a custom location the issue went away.