Maybe someone faced with such kind of problem:
Some images on the website still not indexed by Google (http://prntscr.com/nzb5xp). The very small part was indexed.
Here is one of the examples of the URL where images were published but not indexed: https://besthostadvisor.com/blog/oops-a-server-error-occurred-and-your-email-was-not-sent-007/
Also, the robots.txt file is ok and the rest Cloudflare “Speed” tab сofiguration as well.