SSL错误：UNABLE_TO_VERIFY_LEAF_SIGNATURE

I uploaded my website build with laravel on ubuntu server and used Instamojo to accept payments. I have purchased SSL from Namecheap (PositiveSSL).

The problem is my webhook URL is not working. I tried accessing the URL through Postman and got an error 'Could not get any response'. The screenshot of Postman Console-

This can be caused by failing to bundle the intermediate certificates with the server certificate. You will have at least one intermediate certificate that needs to be bundled with you server cert.

For more information please read the Complete Tutorial for installing SSL on Apache