purple ssh status for some clients 🔗 link

Hi,
we have a huge setup of xymon(nearly 300 clients and a server).Some of the
clients ssh status is purple.it is not updating.
History log says :2009-11-05 12:40:29 Will not update
/opt/xymon/data/hist/a.b.c.d.ssh - color unchanged (purple)-hosts .bbhosts
entry is also ok in hosts file,Wt could be wrong?how to troubleshoot it?

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Pankaj V. Dorlikar