After a replace of old instances, it is not possible to log in in new created instances. The connection gets a timeout, or Permission denied (publickey). (trusty)
See also the diagramm: https://tools.wmflabs.org/nagf/?project=rcm
Maybe this could be a reason:
2015-09-20T12:45:03.442418+00:00 rcm-2 rc.local[371]: #033[1;31mError: Could not request certificate: Connection refused - connect(2) for "" port 8140#033[0m 2015-09-20T12:45:03.442703+00:00 rcm-2 puppet-agent[681]: Could not request certificate: Connection refused - connect(2) for "" port 8140 2015-09-20T12:45:13.443805+00:00 rcm-2 rc.local[371]: #033[1;31mError: Could not request certificate: Connection refused - connect(2) for "" port 8140#033[0m 2015-09-20T12:45:13.444185+00:00 rcm-2 puppet-agent[681]: Could not request certificate: Connection refused - connect(2) for "" port 8140 2015-09-20T12:45:23.445928+00:00 rcm-2 rc.local[371]: #033[1;31mError: Could not request certificate: Connection refused - connect(2) for "" port 8140#033[0m 2015-09-20T12:45:23.446245+00:00 rcm-2 puppet-agent[681]: Could not request certificate: Connection refused - connect(2) for "" port 8140 2015-09-20T12:45:28.164958+00:00 rcm-2 puppet-agent[631]: Could not request certificate: Connection refused - connect(2) for "" port 8140 2015-09-20T12:45:29.368466+00:00 rcm-2 salt-minion[654]: [ERROR ] This master address: 'None' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used 2015-09-20T12:45:29.369155+00:00 rcm-2 salt-minion[654]: [WARNING ] Master hostname: None not found. Retrying in 30 seconds 2015-09-20T12:45:33.447348+00:00 rcm-2 rc.local[371]: #033[1;31mError: Could not request certificate: Connection refused - connect(2) for "" port 8140#033[0m 2015-09-20T12:45:33.447684+00:00 rcm-2 puppet-agent[681]: Could not request certificate: Connection refused - connect(2) for "" port 8140
This was the console output of rcm-2, the console repeat this messages like in a loop. A reboot did not change this. This was a jessie instance.