HI Raghu,
I checkes all the links but no luck, but what I found is when I am trying to run the below URL/Cahce refresh URL more than 4 times PIAFUSER user locking:
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Also I checked in NWA XPI Cahce service (shown in the above Praveens reply) where the above URL confgured and I update PIAFUSER password but still its locking, in Ecahnge profile update PIAFYSER pasword updated using connections.