There are two possible reasons for not being able to set the OID value on a device:
- Policy used to access device is READ instead of READ_WRITE (application settings)
- SNMP configuration on a device itself has no write privileges
To check privileges of a policy go to 
> Settings > Control Panel > SNMP Policies and double click on the policy.
If the problem persist, contact your network engineers to check if the SNMP configuration on a device is READ only.
In order to get the Set OID option, you need to have write or administrator privileges.