What is the content of the .gitmodules file in your projects root directory?
I’m guessing you originally added the submodule for the theme using the firstname.lastname@example.org method, and for some reason, Netlify hasn’t got the right encryption keys to connect to github via ssh. I reckon you should try using https for the submodule (on your local machine) and then see how netlify goes at downloading the theme.
Hi, @AaronNBrock. It could if we still had a valid SSH key to connect to GitHub with. However, after the repo is cloned, our build image immediately forgets the SSH key required for GitHub access. This means that SSH based cloning (even of public repos) will fail. The HTTPS method requires no SSH key and it will still work if the repo is public.
Why do we drop the SSH key after cloning? It is a security measure so that if your site build were somehow to include malicious code, that code wouldn’t be able to steal the SSH key information.
If you do require SSH cloning of private repositories after the initial clone, that can be done. There is documentation about that process here: