Can't read from file

[coret]

I get the following error on https://validator.swagger.io/validator/debug?url=https%3A%2F%2Fwww.openarchieven.nl%2Fapi%2Fopenapi.json

{
   schemaValidationMessages: [
      {
         level: "error",
         message: "Can't read from file https://www.openarchieven.nl/api/openapi.json"
      }
   ]
}

The https://www.openarchieven.nl/api/openapi.json is accessible, but I suspect the swagger-api backend is blocked on the firewall to fend of AI robots. Are the IP-adresses of the swagger-api backend documented somewhere?

Are the two frontend IP adresses the same as the backend servers?

$ nslookup validator.swagger.io
Name:   prod-swagger-oss-public-iac-616114540.us-east-1.elb.amazonaws.com
Address: 54.242.75.89
Name:   prod-swagger-oss-public-iac-616114540.us-east-1.elb.amazonaws.com
Address: 100.49.133.160