There are cases when organizations have firewalls and proxy rules implemented to secure their network, and when they try to use Document Generation or Nintex Sign actions within their workflow, it fails to communicate to these two services and workflow fails.
If you want to use any of the two service, you need to allow following URLs:
1) https://live.nintex.com - Required to perform Nintex license authentication and authorization for access to Nintex External Platform services.
2) https://prdswastrwus01.blob.core.windows.net - Required to upload documents and additional data which are required by Nintex External Platform Services to Azure Blob Storage
3) https://run.nintex.io - Required for outbound requests to utilize Nintex External Platform Services such as Document Generation and Nintex Sign.
4) https://prdswasbuwus01.servicebus.windows.net - Required for inbound requests to resume Document Generation and Nintex Sign related actions using Azure Service Bus