Good afternoon Vijay and welcome to the Events Calendar forum!
Thank you for reaching out to us. We are sorry to hear about issues you are experiencing with Mailchimp.
We would be glad to assist you on this topic.
To be able to offer you proper support however, we would need you to log into your Events Calendar account and use the following link to open up a support thread.
And while you are at it, as a first troubleshooting step, could you please provide us with your system information as well as a copy or link to the broken newsletter ?
The reason for this is because support features and functionalities are limited in the Pre-Sales forum you have used for this thread.
Thank you for your understanding.
For now I will close this thread and we are looking forward to seeing you in the premium plugins forum.
Have a great day!
Geoff B.