A Twitter API error that occurs when you attempt to post a tweet usually indicates a problem with your Twitter account permissions that are connected to your reseller platform. Since your reseller platform is using your own Twitter API credentials, log in to your Twitter Developer account and go to the Application Settings page and click on the API Keys tab.
This problem occurs if you have your access level set to Read Only, which does not allow the API to post information properly. Modify the app permissions to allow Read and Write Permissions, shown below:
Now that these change are completed, save your settings and attempt to send another tweet through your reseller platform. If you encounter any further issues, please contact our Customer Care team.