Why don't preview urls always work?

Question

Telegram

The messenger has support for the OpenGparh protocol, which allows you to conveniently display announcements for urls. But I noticed that not all and not always. Some domains do not.

I did a little research on a number of my sites and found that the preview is requesting TelegramBot
149.154.161.9 - - [26/May/2019:06:01:17 +0200] "GET /temp/og_test2.html HTTP/1.1" 200 52285 "- " "TelegramBot (like TwitterBot)"
But it does not do this to all domains for some reason.
(RKN bans are unlikely here, since sites are not only from the Russian Federation, both with and without previews)

Answer 1

My problems disappeared after moving to another hosting. The IP changed and on the new hosting, the telegram bot began to fully request and create previews.