This error messages comes from Facebook. There may be few reason of it.
1. Your content may be Spammy by Facebook Filter.
2. You have any link attached that blocked by Facebook
3. You are sending message too fast without setting delay.
4. If too much people mark your message as spam.
5. The subscribers from whom it gets the error message is inactive from many days with your messenger.
6. The subscribers who has marked your message as Spam in past.
In past we stopped the campaign instantly if it gets this #368 error.
But we have changed the system a bit.
Now we allow upto 10 error message before stopping the campaign.
Because, it may happen that some people are inactive from your page's messenger from many days or or marked your previous message as sapm. So during sending these people, this error message may come. In this situation upto 10 error , we continue the campign.
After getting 10 error message, we stopp the campaign as completed.
Now goto report, check the error message. If any user get #368 error and if you think , it's not for content issue, but for the inactivity issue, or only for that users of marking spam in previous, then unsusbcribe this leads. So in future campaign he will not be included.
Now in report you will see two button for re-start the campaign & another is Edit button.
So now you can re-start the campaign from where it stopped. Or also you have option to edit your content by clicking Edit button.
Hope this will help you to understand & solve the issue if you face it.