No emails getting through

I would like to ask for your assistance with the issue we’re facing. We’ve been having issues with your plugin since May last year. No emails are being delivered. People are subscribing to our newsletter but they don’t receive the confirmation email so they can’t confirm their subscription. Our newsletter is not being delivered to the existing subscribers either.

We’ve been consulting different IT people and web developers and they all claim the issue comes down to the plugin. We’ve been trying to experiment with other methods of sending in the “Send With…” section but nothing worked, so we changed it back to the “MailPoet Sending Service” but it didn’t solve the issue. 

The “System Status” doesn’t show any errors.

How can we check what happened with all of those emails and why they’re not being delivered?

The page I need help with: [log in to see the link]