Refer Following document to find the exact Reason
http://www.cisco.com/c/en/us/td/docs/security/asa/hw/maintenance/5500xguide/5500xhw/asa_overview.html#87733
You need to get access via console, or any management access will help you find actual cause.
http://www.cisco.com/c/en/us/td/docs/security/asa/hw/maintenance/5500xguide/5500xhw/asa_overview.html#87733
You need to get access via console, or any management access will help you find actual cause.