The error message "Bad Request your campaign is not ready to send" from Mailchimp indicates there's an issue with your campaign that prevents it from being sent. This could be due to a variety of reasons, such as incomplete setup, missing information, or configuration errors. Here are steps you can take to troubleshoot and resolve this issue:

1. Check Campaign Details: Ensure all required fields and sections of your campaign are filled out. This includes the campaign name, subject line, from email address, and content.

2. Review Content: Make sure your email content is complete and doesn't contain placeholder text or missing images. Also, check for any content that may violate Mailchimp's Terms of Use.

3. Recipient List: Verify that you've selected a recipient list for your campaign. If your list is empty or if there are issues with the list (like it's been flagged for high bounce rates), this could prevent sending.

4. Verify Sender Information: Ensure that the sender's information is correctly filled out and verified. Mailchimp requires that the from email address is verified to prevent spam.

5. Check for Errors in the Campaign Builder: Mailchimp's campaign builder will often highlight sections that need attention before you can send. Look for any alerts or warnings.

6. Review Automation Triggers: If this is part of an automated campaign, ensure the triggers are correctly set up.

7. Examine Scheduling Options: If you've scheduled the campaign, double-check the date and time settings. There might be errors or conflicts.

8. Compliance and Terms of Use: Ensure that your campaign complies with Mailchimp's Terms of Use. Issues like incorrect audience permission settings or content that's against policy can prevent sending.

9. Contact Support: If you've gone through all the above steps and still face issues, reach out to Mailchimp support for assistance. They can provide specific guidance based on your account and the campaign in question.

10. Consult Mailchimp's Help Center: Mailchimp's Help Center contains detailed guides and troubleshooting tips for various issues, including sending campaigns.

To resolve the issue efficiently, it's often helpful to start with the most common problems (like verifying campaign details and checking the recipient list) before moving on to more complex troubleshooting steps. If you're new to Mailchimp or managing large campaigns, take extra care to review their guidelines and best practices to avoid common pitfalls.