API calling failures may occur in three scenarios: within a VPC, between VPCs, and on a public network.
For details about how to create and use VPC peering connections, see section "VPC Peering Connection" in the Virtual Private Cloud User Guide.
Bind an EIP to the API and try again. For details, see section "Creating a Gateway" in the API Gateway User Guide.
For details about how to configure inbound rules, see section "Creating a Gateway" in the API Gateway User Guide.
Check whether the API has been published. If the API has been modified, publish it again. If the API has been published to a non-RELEASE environment, specify the X-Stage header as the environment name.
If the API uses app authentication, check whether the AppKey and AppSecret used to call the API are correct.