SSH DSA key support is not recommend and disabled per default since 2015 on openssh upstream release beacuase of weakness of the algorithm.
So, We will stop to support of DSA key for OSDN ssh login.
You can check SSH keys you registered above url. If you have ssh-dss key, the key will not accept to use login for OSDN after Jan. 2019. You should use another typo of key.