Bulk Emails Not Being Received After Update

Emails are still being sent out on normal notifications, but our bulk email system is not working ever since the latest update. For context: we have already spoken with our host (bluehost) and there is no limit on how many emails we can send per hour as we have a private server.

The server times out when we are trying to send out emails (this didn’t happen before). Any suggestions? Also until there is a fix, is there anyway we can downgrade to old plugin version?

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