@Kirill Gromov Good morning.
Host tech support response:
We tried to upload a file to your site with a gif image ourselves, and received the following:
You did not pass the security check. Please try again.
And these are the logs we have:
2023/11/09 00:13:52 [error] 41100#41100: *26220798 upstream prematurely closed connection while reading response header from upstream, client: 35.91.232.102, server: site.ru, request: "GET //site.ru/uploads/javascript_global/root_front.js HTTP/1.1", upstream: "http://127.0.0.82:80//site.ru/uploads/javascript_global/root_front.js", host: "site.ru"
Would that help in any way?