Problems with Validator

Trying to use the validator for testing various resources. I am getting errors about various URLs aren’t resolving. For example:
Canonical URL '' does not resolve

If I drop this url in my browser, it resolves just fine.
I’ve tried setting the java environment variable to use my system proxy settings
(, and including my proxy as an argument (-proxy …), but no luck.

Am I missing something?

If you want to perform validation that depends on artifacts from an implementation guide, you need to pass a “-ig” parameters to the validator listing the relevant IG(s). Without that, the validator only has awareness of the content defined in the FHIR core specification for the specified version.