Uncaught Error: Undefined constant “WPW3ALL_MAIN_DBPREFIX”

Hi team,

In the last version of the plugin, the 2.6.7, I obtain an error in the WordPress login, in the server log I found:

[Fri Dec 23 21:59:06.736719 2022] [proxy_fcgi:error] [pid 909351:tid 139835072587520] [client XXX.XXX.XXX.XXX:20482] AH01071: Got error 'PHP message: PHP Fatal error:  Uncaught Error: Undefined constant "WPW3ALL_MAIN_DBPREFIX" in /var/www/site.com/wp-content/plugins/wp-w3all-phpbb-integration/class.wp.w3all-phpbb.php:788\nStack trace:\n#0 /var/www/site.com/wp-content/plugins/wp-w3all-phpbb-integration/class.wp.w3all-phpbb.php(2942): WP_w3all_phpbb::phpBB_user_session_set()\n#1 /var/www/site.com/wp-content/plugins/wp-w3all-phpbb-integration/wp_w3all.php(585): WP_w3all_phpbb::phpBB_user_session_set_res()\n#2 /var/www/site.com/wp-includes/class-wp-hook.php(308): wp_w3all_phpbb_login()\n#3 /var/www/site.com/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()\n#4 /var/www/site.com/wp-includes/plugin.php(517): WP_Hook->do_action()\n#5 /var/www/site.com/wp-includes/user.php(110): do_action()\n#6 /var/www/site.com/wp-login.php(1231): wp_signon()\n#7 {main}\n  thrown in /var/www/site.com/wp-content/plugins/wp-w3all-phpbb-integration/class.wp.w3all-phpbb.php on line 788', referer: 

Mi site is a multisite and in the code I don’t find the point where there is the constant WPW3ALL_MAIN_DBPREFIX and there are a lot of code in the form of:

(is_multisite()) ? WPW3ALL_MAIN_DBPREFIX . 'users' : $wpdb->prefix . 'users';

Maybe there is something missing?

Thanks and regards.
G.