Looking at system condition monitor the time column for the SSID being monitored displayed TIMEOUT as shown below:
Condition System Condition Monitor Item 1-1/1
Actions: S=Show Detail, X=Except, T=Threads, A=Subsystem Stats
Show
* DB2 CPU3 Inactive N Excpt X X X
Name Type System Time Count Condition
-------- -------- -------- -------- -------- ---------------
. DB2D DB2 CPU3 Timeout 0
Recycling the GSS started task resolved the problem.