If snmpwalk isn't responding then you need to fix that.
1. Is your device reachable over the network? (Can you ping it?)
2. Does your device have its SNMP agent enabled?
3. If your device has an SNMP ACL, does it allow access from the address you are querying from?
4. Are you using the same version of SNMP query that the agent has enabled?
5. Are you using the correct credentials? (e.g. v2c community string, or v3 authPassword/privPassword)
Once all of 1-5 are correct, your device should respond.