Please update wpForo to the latest version. The version you're using doesn't support multisite. 

I'm getting this PHP error in a wordpress multisite install:

WordPress database error Table 'wordpress.wp_3_users' doesn't exist for query SELECT COUNT(*) FROM `wp_3_users` made by require_once('C:\inetpub\wwwroot\wp-admin\admin.php'), require_once('C:\inetpub\wwwroot\wp-load.php'), require_once('C:\inetpub\wwwroot\wp-config.php'), require_once('C:\inetpub\wwwroot\wp-settings.php'), do_action('init'), WP_Hook->do_action, WP_Hook->apply_filters, wpForo->init

In wpforo.php you have these two lines in the function "init":

  $users = $this->db->get_var("SELECT COUNT(*) FROM `" . $this->db->prefix . "users`");
  $profiles = $this->db->get_var("SELECT COUNT(*) FROM `" . $this->db->prefix . "wpforo_profiles`");

In the second line the table exists (wp_3_wpforo_profiles), as we have a table for each site for wpforo profiles, but there is only one general wp_users table so PHP returns that error.

Thank you very much for your great plugin!