Executing '/call start' Command API Does Not Initiate Call in Private Channel

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Summary

While utilizing the "Execute a command" API to trigger '/call start', I successfully receive a status code of 200. However, the expected outcome of initiating a call in a private channel does not occur.

Steps to reproduce

Server URL: https://community.mattermost.com version from my mobile app:

Server Version: 9.0.0 (Build master)
Database: postgres
Database Schema Version: 110

Create a private channel.
Execute the login API to obtain an authentication token.

Utilize the "Execute a command" API with the following payload:

{
  "channel_id": "the-private-channel-d",
  "command": "/call start"
}

Expected behavior

The anticipated behavior is for a call to initiate within the private channel.

Observed behavior (that appears unintentional)

Currently, no action takes place within the private channel. Despite receiving a status code of 200, the response appears as follows:

{
    "response_type": "",
    "text": "",
    "username": "",
    "channel_id": "",
    "icon_url": "",
    "type": "",
    "props": null,
    "goto_location": "",
    "trigger_id": "c63ihapk7brqfxajnr37d5g5kc",
    "skip_slack_parsing": false,
    "attachments": null,
    "extra_responses": null
}

Additionally, I attempted the same process with a direct message channel_id, which resulted in a 403 status code, even when using simpler commands such as "/echo test".

mattermost / mattermost-plugin-calls