MailChimp & Bigin Integration doesnt work for 2nd Audience

MailChimp & Bigin Integration doesnt work for 2nd Audience

We are trying to migrate from MailChimp to Zoho Campaign, for this we are trying to sync all contacts from MailChimp to Zoho Campaigns via Zoho Bigin.

The 1st sync got configured, but 2nd & 3rd Sync is not getting setup.  Once I click on the activate button, it just keeps on working, and it never completes, even after 2hr.