I could successfully access the API using the HTTP Retriever node. You can just input the given URL https://api.weather.gov/zones?area=CO&type=land&include_geometry=true into the HTTP Retriever node, no need to escape anything. The accept header is not strictly necessary, it’ll send JSON per default (for APIs which require a specific header, you can use the “Headers” tab of the node).
if you paste your link into a browser it will show you the error. Your link is faulty with the empty id parameter just remove that like qqlihq did then the GET node works just fine.