I had snmp configured and all was working and one of the router just decided not to respond any more, restarting did not help. any idea what could gone wrong suddenly ? 6.33.1

Are you sure the SNMP traffic is still getting to the router? Check using Torch to see if there is any incoming traffic for port 161. If there is RX for SNMP, is there all TX when using Torch? Do you have your SNMP restricted to only a few IP addresses, and your server's IP has changed? Or did your routers IP address change?

on the same link i have 6 other routers and they are all responding fine, nothing changed, and i have no restriction on IP for snmp, as externally the snmp is blocked, i will try and see if traffic is responding.