I believe the Digi One SP does not offer SNMP functionality.
First, SNMP is not listed on the spec sheet of this product. I also looked at a unit of my own (with newer firmware, 82000774_W) and did not see any mention of SNMP. In the Web UI, under Configuration / Security, Network Security, all of the available services are listed, and SNMP is not there. Additionally, if you "CLI" into the Digi One SP, i.e. through telnet, and issue the "show service" command, SNMP isn't listed there either.