I am getting the following message frequently when trying to open DSM Explorer:
"The AM Manager does not respond. Please check if the AM Manager is running."
Although there are many possible causes for this error to occur, one of the most likely ones is a short timeout for the Admin Console.
Client Automation - All versions
Increase the Admin Console timeout.
Update the default configuration policy or create a new one, seal it and publish it.
The policy value to change is:
/Domain/Control Panel/Configuration/Configuration Policy/<>/DSM/Administration Console/Session Messaging Timeout
Increase it to 600 and try if the problem persists.