Hi Raza,
I have seen couple of issues around this earlier.
Their is not one particular reason we can point to and need to look from many aspects.
1. Check if <Machine_Name>__CatalystConnector is showing on the WebUI, if not then need to look at ..\CA\Catalyst\CatalystConnector\ifw\log\ifw.log
2. If this entry is showing but SCOM connector is not shwoing then need to look at connector log in location ... CA\Catalyst\CatalystConnector\container\data\log
Thanks,
Ashay