Error processing integration response

The response body could not be converted to an Appian value
The jsonText parameter was not valid JSON. Received:

Question

First Scenario: 
 I have created a "GET" web API in Appian Community Edition and called it through a integration from another Appian environment, but I receive body in the "HTML" format instead of Json and receiving below error. 
 Second Scenario: Whereas, When I create it other way around like creating web API in other Appian environment and calling it from Appian community Edition returns a proper Json value in the response body. Why I am receiving "HTML" value in response body in First Scenario, it is like Appian community Edition doesn't support web APIs?

Shubham Aware · Answer

Integration is not properly authenticated when calling the Appian Community Edition web API. Instead of returning the JSON data, Appian sends an HTML login or error page. The main causes are usually missing or incorrect authentication (such as lacking API keys or user credentials) or insufficient permissions for the account making the request. To receive a proper JSON response, ensure you use the correct authentication method and that the user or service account has the necessary access to the API. Or Community Edition doesn't support external web API calls properly. Community Edition has "DevOps, Infrastructure, and Import/Export features disabled", causing APIs to return HTML instead of JSON when called externally. Community Edition can consume external APIs but cannot serve them to external systems. You need a paid Appian environment for full web API functionality.

Error processing integration response The response body could not be converted to an Appian value The jsonText parameter was not valid JSON. Received: <...