protobox: Bitbucket rejects public key

Carrying on from my previous woes, bitbucket rejects my public key. I’ve verified that it gets copied across from my data/ssh folder, but I still get the following:

TASK: [repository | git | install git application] **************************** 
failed: [localhost] => (item={'path': '/var/www/3dpixel.net/httpdocs', 'name': 'Maybestand', 'install': 1, 'options': {'pre_install': [], 'source': 'git@bitbucket.org:snetty/maybestand.git', 'provider': 'git', 'post_install': [], 'revision': 'master'}}) => {"cmd": ["/usr/bin/git", "ls-remote", "git@bitbucket.org:snetty/maybestand.git", "-h", "refs/heads/master"], "failed": true, "item": {"install": 1, "name": "Maybestand", "options": {"post_install": [], "pre_install": [], "provider": "git", "revision": "master", "source": "git@bitbucket.org:snetty/maybestand.git"}, "path": "/var/www/3dpixel.net/httpdocs"}, "rc": 128}
stderr: Warning: Permanently added the RSA host key for IP address '131.103.20.168' to the list of known hosts.
Permission denied (publickey).
fatal: The remote end hung up unexpectedly

msg: Warning: Permanently added the RSA host key for IP address '131.103.20.168' to the list of known hosts.
Permission denied (publickey).
fatal: The remote end hung up unexpectedly

FATAL: all hosts have already failed -- aborting