Drupal 7. White screen after death after trying to login to admin?

Question

Drupal

If you reset the cookie, then the site opens and works, but if you try to enter the admin panel, then only a white screen remains and that's it. The entire site becomes inoperable.
Version php 5.5
I tried to insert the following code in index.php:

error_reporting(E_ALL);
    ini_set('display_errors', TRUE);
    ini_set('display_startup_errors', TRUE);

The site is on shared hosting, I looked at the logs, there

[Fri Sep 02 03:48:55 2016] [error] [client 92.126.20.152] File does not exist: /var/www/u4332058/data/www/site.ru/favicon.ico, referer: http://site.ru/

but I do not think that the absence of a favicon affects the operation of the site.
What could be the problem ? I tried restoring backups, still the effect is the same, although the site was working fine a week ago.

Answer 1

Enough operatives?