By default, after a server is down for an hour it is removed from the Spectrum OneClick view. This is due to the map entry timeout value removing the landscape from the landscape map.
There is a map entry timeout value that is used to determine when the landscape should be removed from the map when it is not contactable. You can update the timeout value by modifying the <SPECROOT>/LS/.locrc file and adding:
The value needs to be set in milliseconds. The default is set to 1 hour (3600000 milliseconds = 1 hour). It sets the interval to remove the landscape from the landscape map, which in turn removes it from OneClick.