Probably just a cosmetic issue, but restarting all services as it says in sk111944 to resolve it is a bit of a blunt force instrument.
Generally when you are retrieving status from a gateway, the updates are provided by the cpd daemon on the gateway. If that daemon is having issues it may log something into $CPDIR/log/cpd.elg that is helpful. However I have seen restarting just the cpd daemon on the gateway clear a number of status issues (and doing so will not cause an outage). Obviously this is not a long-term solution but can help identify where the problem is located.
There is also a daemon called cpstat_monitor but I believe that one is just for the advanced Traffic/System Counters reports provided by the monitoring blade and not for general status.
Finally there are a number of status databases maintained by cpd that can get corrupted in various ways (such as the SMS running out of disk space) causing strange status behavior. The primary indicator of this condition is high CPU utilization by cpd or it occasionally crashing. See these SKs:
sk101484: CPD is consuming high CPU utilization (>90%) or CPD is terminated on the Security Gateway
sk109940: CPD daemon consumes CPU at high level and exits periodically.
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