I think the issue is you cloned out the repository, but not the submodule in core.
core
Assuming you used the command-line, this should help you: https://stackoverflow.com/questions/3796927/how-to-git-clone-including-submodules
@Gordon started
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I think the issue is you cloned out the repository, but not the submodule in
core
.Assuming you used the command-line, this should help you: https://stackoverflow.com/questions/3796927/how-to-git-clone-including-submodules