As of April 9, 2019, Facebook no longer allows a pre-checked state for the checkbox. You can read their official announcement in this article
Why is Facebook making this change?
The pre-checked state caused confusion for some customers that were surprised to receive messages in Messenger. Because the checkbox was pre-checked, some customers didn't know they were opting-in for updates and were unhappy when they received messages from brands. Facebook ultimately decided to remove the ability to pre-check your checkbox.
How does this affect my store?
This means that if your store had the pre-checked checkbox before, as of April 9th, it is no longer pre-checked, and your site visitors have to check it manually in order to subscribe for updates.
However, we have a lot of other features that can help you gain more followers and increase your revenue.
Here are some options:
The welcome pop-up which opts users in on a pop-up on your site. If they click the button to receive a discount they will be opted in.
The customer chat widget which embeds the bot directly on your site. If customers start chatting with the bot, they will be opted-in.
Opt in more people by letting customer sign up for order confirmations and shipping notification updates from the order status page
You can check out this article where you can find more info on those features:
Is this true just for Octane AI or any platform?
This new rule applies to all bots and platforms which means that no one will be able to have the checkbox pre-checked any longer.