There can be many reasons if the client connection fails or hangs, but these are some of the common reasons:
Services fail to start during restart
Permissions applied by group policies to the server If the casuser, which is the Cisco Security Manager (CSM) managing user, does not have proper access to the resources on the box, then problems can ocurr.
Misspelled server name upon rebuild
Device Credentials Repository was damaged
Networking devices such as a firewall that can block access
In order to resolve this issue, restart the Daemon Manager. Wait for five to 10 minutes after the services appear, and then use the resetcasuser utility command in order to make sure the permissions are correct on the server.
In order to use the resetcasuser utility, complete these steps:
Stop the Daemon Manager.
Choose Program Files > CSCOpx > Setup > Support.
Run resetcasuser.exe. Choose 1 in order to have a random password generated, and choose 2 in order to set your own.
If none of these help, in most cases CSM must be rebuilt.