Xymon conn icon shows white, rather than green

I recently setup a Xymon server.  After turn on, the web page all the
"conn" item shows white, rather than green: 
(I only put contents on hosts.cfg and /etc/hosts files, not going deep
into any other configuration yet). 
 
 
When I use fping, it shows the server is alive: 
 
[root at island-vm etc]# fping BOOMIAPP01

BOOMIAPP01 is alive

 
Where is the configuration file to control it?