Strange issue with custom poller on a Cisco Catalyst 1900

I have two old Cisco Catalyst 1900 switches for which I am trying to configure custom pollers using the UnDP tool. The are OIDs in the MIB walk for both switches in the region of 1.3.6.1.4.1.437.1.1.3.3.1.1.3. However, as you can see in the screenshot, when I test against one of the switches, I get the "No value was returned" response. One can clearly see the OIDs in the MIB walk, so what is going on here?

Thanks for any help.