Restart service sshd on the client and installation server:
service sshd restart
From the Installation Server open an ssh session to the client(s) (this is necessary to do only one time, for the certificate to be recorded on the installation server, and so it does not ask again if the connection is secure or not):
Edit file ".omnirc" on the installation server, adding the variable:
OB2_SSH_ENABLED = 1
Restart (if necessary) Data Protector services.
Try again to deploy the agents... it should use ssh without any problem.