Dear Support! I installed Multi-DB plugin and configured

Dear Support!

I installed Multi-DB plugin and configured in this tutorial:
https://premium.wpmudev.org/project/multi-db/#usage
I would like to activate the plugin, in screen write Plugin activated, but in the plugin list label not change Deactivate.
This is the Nginx log in:
PHP message: WordPress database error Incorrect table name '' for query UPDATE '' SET option_value = 'a:1:{i:0;s:15:\"multi-db/d
b.php\";}' WHERE option_name = 'active_plugins' made by activate_plugin, update_option, m_wpdb->query"

Installed program:
- php 5.4.4
- mysql 5.5.38
- nginx 1.2.1
- wordpress 3.9.2

I set 3 sites, subdomain.

Please help me!
Thank you.