git@github.com: Permission denied (publickey) - during submodule clone

[j143]

ubuntu@ip-10-0-0-4:~/repo/systemds$ git submodule update --init --recursive
Cloning into '/home/ubuntu/repo/systemds/src/main/cuda/ext/jitify'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

fatal: clone of 'git@github.com:corepointer/jitify.git' into submodule path '/home/ubuntu/repo/systemds/src/main/cuda/ext/jitify' failed
Failed to clone 'src/main/cuda/ext/jitify'. Retry scheduled
Cloning into '/home/ubuntu/repo/systemds/src/main/cuda/ext/jitify'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.