Mail Chimp expert

Not sure if this is something you can help with? We have installed a new firewall on our wordpress site - since installing we cannot connect our mailchimp account? Our site can see mailchimp through the API but mailchimp gives back a 403 error cant connect. I have gone back and forth between mailchimp and host and cannot fix -IS THIS SOMETHING ANYONE HAS EXPERIENCE OF?

Oops, we're getting an error back from your site (https://www.getdynamicanddigital.com returned a 403 status code).