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.
I'm facing issue with CIDR.
I made some tests with 8.8.8.8, it's working properly but not with 8.8.8.0/24 notation.
Did I miss something ?
The only CSV I can think of for the app is the one you set up under "Configure" in the app (shodan_lookup.csv), which absolutely supports CIDR notation.