Hi @raylinuk and welcome to the Community!

The purpose of the Double Opt-in feature is to send a confirmation email upon sign-up, so if I understand the issue correctly and you’ve turned it off, subscribers will no longer receive confirmation emails. You can turn this feature back on via your List Settings tab. 

Here’s another Community thread discussing the same topic:

Alternatively, if you were looking to receive a notification every time someone else fills out your form, I’d recommend the following Community posts on the topic:

I hope this helps, and thanks for using the Community!

-Brian