Is your monitor type appropriate, there is a certain case where the monitor type applied is incorrect when using the Citrix iApp. If your monitor type correctly matches the pool service, I would verify your host settings on your IIS server match up with your monitor host string. When using http service, if you leave the host name blank for the binding on your IIS app server, then the host string in your monitor does not matter. However, if you specify a host name in the bindings setting on your IIS server to a specific host name, then your monitor string has to match. Another item you can test is to leave the application field blank when filling out the iApp, doing so will leave the receive string blank for your XMl monitor. If your monitor shows an up status with a blank receive string, then you may have entered the wrong text for you published app - the monitor is case sensitive. Verify your xml monitor receive string is set as the display name of the application being monitored.
Nimbostratus