Correct a Wordpress Mailchimp Plugin Glitch

I am looking for a freelancer who can help me with a specific issue I am experiencing with the Mailchimp plugin on my WordPress website.

Issue:
- The integration of the Mailchimp plugin (Chimpmatic) is not working properly. The plugin is used to capture email addresses from out Contact Form 7 submissions and dump the data into our Mailchimp account. However, after a developer corrected an issue with another, unrelated, plugin, the Mailchimp plugin stopped working. The previous developer has dropped contact after I described the issue and we are left not knowing what he did to cause the problem.

Requirements:
- Experience with WordPress plugins and Mailchimp platform.
- Knowledge of troubleshooting integration issues.
- Familiarity with the latest version of WordPress and Mailchimp.

Skills:
- WordPress plugin development
- Mailchimp integration
- Troubleshooting

Please note that I do not have any error messages or error codes related to the issue. The freelancer should be able to diagnose and fix the integration issue without relying on error messages.

This is the Mailchimp plugin we're using: https://chimpmatic.com/

If you have experience with WordPress and Mailchimp plugin, and are familiar with the latest version, please apply for this project.