There could be several reasons why your notify_push function might not be successfully delivering messages to a WeChat group:

1. Check URL: Ensure that the URL specified in the url parameter ('https://www.baidu.com') is valid and correctly formatted. If you're using the 'webhook' channel, this URL should be capable of receiving POST requests with message data.

2. Verification Code: Sometimes after setting up a webhook for receiving messages on your server, there might be a verification process or code that needs to be implemented in order to confirm the webhook setup is correct and functioning properly.

3. Webhook Setup: If you're using 'webhook' as the channel parameter and not 'wxpusher', make sure your server correctly processes POST requests sent from notify_push. This includes handling the content sent within the payload according to the message type specified (in this case, 'text'). The payload's msgtype should be set appropriately for it to handle text messages.

4. Access Control: Check if there are any access restrictions or permissions issues that might prevent your application from posting messages through either the webhook or WeChat Push services.

5. Coding Errors: There could potentially be errors in how you've implemented the notify_push function call, such as incorrect parameter order or a typo in method names. Ensure you're using the correct function name and parameter names provided by the API documentation.

6. Server Configuration: If your application server isn't configured correctly to receive incoming POST requests and handle them properly, this could also result in not receiving messages.

7. API Limitations or Errors: There might be limitations with WeChat's API based on usage patterns, quotas, or issues with their backend services that temporarily prevent message delivery.

8. Debugging Tools: To help diagnose the issue, you could implement logging and debugging within your server-side code to see if it receives any POST requests from notify_push and logs the content of those requests. This can provide insight into where things might be going wrong in your application's processing of messages.

To specifically address the 'webhook' channel not working as expected:

• Verify your webhook setup: Ensure that you've correctly configured your server to listen on the specified URL for incoming POST requests.
• Debug with logs: Look at any error messages or debugging output that might help pinpoint issues in your server-side code. Check if notify_push is even triggering the webhook response from your application.
• Check payload structure: Make sure that the payload object is correctly structured to match what your server expects. For example, ensure that msgtype is set as 'text' and that the content field contains a string of text.

If you're still unable to diagnose or solve the issue after checking these aspects, it might be helpful to consult with a developer familiar with API integrations or reach out to WeChat's support for assistance specific to their platform.