Why the device can not be appeared!

I add an network 200.200.200.0/24 to search,in this network,there only have two devices,one is Cisco 2950 Switch,another is Cisco 2600 Router.twenty minutes elapse,I want to go to "Infrastructure Views>Routers" to see Cisco 2600 Router ,but there is empty,no icon of Cisco 2600 Router,then I go to "Infrastructure Views>Switches" to see,there has an icon of Cisco 2950 Switch, last, I go to "Network Views>200.200.200.0" to see,there is only one device icon which is Cisco 2950 Switch icon.
So,I input the IP address 200.200.200.2 in "Device Search" to serach Cisco 2600 Router,at this time,Opmanager provide the snapshot of Cisco 2600 Router to me,then I go to "Infrastructure Views>Routers" and "Network Views>200.200.200.0" to see,but find these two places are no icons of Cisco 2600 Router too.
Strangely,I restart the Opmanager,then go to the same palces,and find the icons of Cisco 2600 Router.
Why?Can support-team help me to find out this reason?????