How to understand why https is crossed out?

Question

Digital certificates

Please tell me where to start. All browsers except Chrome are fine.

Answer 1

Start by reading this article:
habrahabr.ru/post/236373
Recent versions of chrome consider using SHA-1 not safe.

Answer 2

You can analyze the security of the SSL server here: https://www.ssllabs.com/ssltest/
It will tell you not only about problems with the certificate, but also about weak algorithms that can be used.