ssh-add gives error message: Could not open a connection to your authentication agent.
This is because your ssh-agent has stopped running for some reason and is unable to restart automatically. Try removing the following file on PUMA:
puma$ rm ~/.ssh/environment.puma
Then log out of PUMA and back in again. You should then see a message similar to:
Initialising new SSH agent...
And you should then be able to run ssh-add successfully.