Thank you Charles, I tried it first - I mentioned it above. Yes HTTP goes, but it's not a solution, just a test.

My server certificate is Let's Encrypt and is valid. As I mentioned, the server does not register any blocking or certificate errors (they have nginx, which has its own status on cert error) - on the contrary the status is 200 (request is OK).

If it is to be in the certificate, then just how Word 2016 32-bit works with it - where can I find out and control the way Word works with certificates? I repeat that Word 2016 64-bit + HTTPS is a functional combination. Can 32-bit have different rules for public certificates than 64-bit?