When setting up LINE channel in the Conversation API on the Sinch Dashboard, your LINE bot webhook callback URL will be auto configured upon saving the token and secret. But if you have not yet enabled "Use webhook" then you will receive a message that the callback URL is disabled.
Here is how you can turn on "Use webhook" on the LINE Developer Center
The Sinch Developer Documentation site contains comprehensive documentation and tutorials, which show you how we support LINE through the Sinch Conversation API.