While looking into a Active/Standby Cisco ASA that gave me the error below
Unable to launch device manager from X.X.X.X
After looking into this issue I found that it attempted to switch between active and standby. The message was switching failed in the standby log. The cert was still present when going to this in a browser but all pages returned 404.
Quick step was switching to standby to active. This allowed changes to be applied from the ASDM. After reloading the standby at this point found this message during boot.
!!!!!....Device Manager image set, but unable to find disk0:/asdm-635.bin
To fix this assure the ASDN has been copied to your standby ASA. I use Open TFTP Server from source forge to manage ASA updates. http://sourceforge.net/projects/tftp-server/
CLI commands for copying off the asdm from the upgraded ASA
copy flash:/asdm-XXX.bin tftp:/
Copy ASDM to other ASA
copy tftp:/asdm-XXX.bin flash:/
For me I did not have to restart the standby ASA after loading the ASDM bin file.