Notifications only sent to some subscribers (and that not everytimt)

For a while now not every subscriber get the dayly notification. Deinstalled and reinstalled subscribe2 but that didn’t solve the problem. Nay idea what I can do? Here is what I get in my WordPress log:

[31-May-2021 06:08:26 UTC] PHP Notice:  Undefined index: feedkey in /PATH/wp-content/plugins/members-only.php on line 251
[31-May-2021 06:08:26 UTC] PHP Notice:  Undefined index: feed in /PATH/wp-content/plugins/members-only.php on line 296
[31-May-2021 06:08:26 UTC] WordPress-Datenbank-Fehler Unknown character set: 'utf8_general_ci' für Abfrage CREATE TABLE wp_autofreisubscribe2 (
			id int(11) NOT NULL auto_increment,
			email varchar(64) NOT NULL default '',
			active tinyint(1) default 0,
			date DATE default '2021-05-31' NOT NULL,
			time TIME DEFAULT '00:00:00' NOT NULL,
			ip char(64) NOT NULL default 'admin',
			conf_date DATE,
			conf_time TIME,
			conf_ip char(64),
			PRIMARY KEY (id) ) DEFAULT CHARACTER SET utf8_general_ci von require('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('plugins_loaded'), WP_Hook->do_action, WP_Hook->apply_filters, S2_Core->s2init, S2_Upgrade->install, maybe_create_table