The Startup type for the ASP.net State Service must be set to Automatic.
Automatic
Click the Fix it link next to this missing prerequisite to have Kaseya Server Setup fix it for you.
ASP.NET State Service: 7 and 8
ASP.NET State Service: XP, 2003 and 2003 R2
ASP.NET State Service: 2008, 2008 R2, 2012 and 2012 R2