I also faced the same problem. Hurricane labs app is querying Shodan and providing the results. I figured out in my case, the API is broken. Shodan REST API documentation (link below) specifies that net filter to be used for the CIDR notation. However, I know the API key works as I tested with the 4.2.2.2, but it wont work for CIDR, for ex: query=net:4.2.2.0/30 (which ideally should return the results)
https://developer.shodan.io/api
You can try this on your browser with your API key and query as per the document.
https://api.shodan.io/shodan/host/search?key={YOUR_API_KEY}&query={query}
I presume if this gets fixed then the app will work for CIDR.
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