From: DeskNow Knowledge Base
http://www.desknow.com/kb/

DeskNow is not starting. What do I do?
http://www.desknow.com/kb/idx/12/039/article/

There are many possible causes on why DeskNow is not starting.

The best way to find out is, in order:

Try to login. If DeskNow started the HTTP interface only, it will display an error message explaining what error prevented it to fully start. This error will also appear in the log.Init log file (in C:desknowdatalog or /var/desknowdata)

If no HTTP interface is available, the most likely cause of the problem is that another web server is using the HTTP or HTTPS ports. Check these two articles on how to integrate DeskNow with IIS and Apache:
http://www.desknow.com/kb/idx/12/035/article/ (IIS)
http://www.desknow.com/kb/idx/12/035/article/ (Apache)

If you are running on Linux, try starting DeskNow in console to see any error message, using the following command:
/var/desknow/bin/catalina.sh run

If you are running DeskNow in Windows, try starting DeskNow in console instead of as a Windows service. This can be done by selecting 'Start DeskNow in console' in the Advanced submenu of the DeskNow program group. If DeskNow can start in console, but not as service, see http://www.desknow.com/kb/idx/0/030/article/

If you are running DeskNow in Windows, reasons on why DeskNow is not starting even just the HTTP interface can be found in the log files of the HTTP engine (Tomcat), available in C:Program FilesDeskNowlogs

Another common error is  "DeskNow did not start correctly because of the following error:
The SMTP port (25) is in use by another application."

This is explained in more details in this article:

http://www.desknow.com/kb/idx/12/050/article/