Why the Autoresponder emails are not arriving?

Secondly, the emails are definitely not in the junk mailbox. Those who used to get the autoresponder are also no longer receiving it. This has only happened since I tried to integrate Trello. 

I tested this issue on my test form and everything worked fine, both, Notification and Autoresponder were sent. And the card was created in Trello.

I checked with my colleague Welvin, he received the Autoresponder when he submitted your form.

Also, I checked this email from your submission: delliott@cmri.org.au.

The email is marked as sent.

Do you have an example email address that failed in receiving autoresponder?

It works now :)

Not sure what was happening. Must have been fixed when Welvin sorted out the issue with the Trello integration!