Why doesn't QIWI API accept SSL from Let's Encrypt?

Question

Qiwi

I want to connect Qiwi payment acceptance to the site. I did invoicing by API, but I had problems getting a notification from the kiwi side. The documentation says that notifications are sent only to sites where SSL is installed from trusted certificate authorities. Otherwise, you want the server to send the complete chain of certificates, including the trusted root CA at the beginning of the chain.
Has anyone connected the QIWI API to a site with SSL from Let's Encrypt? How did you solve this problem?

Answer 1

- Check if the certificate is installed correctly here: https://www.ssllabs.com/ssltest/
- OR periodically make requests to QIWI yourself to check the payment status. The documentation recommends this option.