For Security reasons Facebook, customer chat plugin renders only on the Websites that are whitelisted within the relevant Facebook page.
Whitelist Domain Name
From your Facebook page
Click on ‘Settings’
Click on ‘Messenger Platform’ tab
Scroll down the page – you can notice ‘Whitelisted Domains’ options
Add full qualified domain name,
For E.g – https://example.com/
Website must server from ‘https’ protocol.
Add the domain name that serves over HTTPS,
If SSL Certificate is not installed add domain name without HTTPS also, this may work.
Add Fully Qualified domain name. Adding Localhost, IP address may not support.
Add the domain name, how your website is loading.
To Avoid Confusion
Its better to add with http and https versions – http://yourdomain.com, https://yourdomain.com.
Adding domain with “www” is like adding a subdomain, if you are accessing your website without “www”, add a domain name without “www”
Adding domain name in multiple ways won’t cause an issue like http://example.com, https://example.com, https://www.example.com