Error with ssl cloudflare on ubuntu 16.04 apache2, how to solve?

Question

cloudflare

I bought a domain, redirected to cloudflare, enabled ssl (full) and got 521 errors. Further opened the 443rd port, received the 525th error. With flexible, everything works, but in
general I don’t know what to do. I tried to make a certificate through Let's Encrypt, it didn't work (didn't work).
Tell me what to do?

Answer 1

Your certificate is normal, check the css and images on the site, they must be connected via https