Error

No notifications are sent.

The system tab shows this:

SITE_URL:                 https://robertvanbregt.nl/wp
HOME_URL:                 https://robertvanbregt.nl

CKPN Version:             1.9.4
WordPress Version:        4.9.8

PUSHOVER NOTIFICATIONS SETTINGS:
application_key: [removed for display]
api_key: [removed for display]
new_user: false
new_post: false
post_notification_role: administrator
new_comment: true
notify_authors: false
password_reset: false
plugin_updates: false
core_update: false
sslverify: false
multiple_keys: false
logging: true

ACTIVE PLUGINS:
Akismet Anti-Spam: 4.0.8
Bridgy: 1.4.2
Hum: 1.2.2
IndieAuth: 3.1.2
IndieWeb: 3.3.8
IndieWeb Press This: 1.0.4
JSON Feed (jsonfeed.org): 1.1.2
Micropub: 1.4.3
Post Kinds: 3.0.9
Press This: 1.1.1
Pushover Notifications for WordPress: 1.9.4
Semantic-Linkbacks: 3.8.1
Simple 301 Redirects: 1.07
Simple Location: 3.3.8
Syndication Links: 3.4.1
Webmention: 3.8.2
WebSub/PubSubHubbub: 3.0.0

CURRENT THEME:
ZenPress: 1.0.0-dev

Multi-site:               No

ADVANCED INFO:
PHP Version:              7.1.20
<strong>MySQL Version:            <br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined function mysql_get_server_info() in /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-content/plugins/pushover-notifications/includes/admin/admin-pages.php:280
Stack trace:
#0 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-content/plugins/pushover-notifications/pushover-notifications.php(235): ckpn_display_sysinfo()
#1 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-includes/class-wp-hook.php(286): CKPushoverNotifications->determine_tab('')
#2 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters('', Array)
#3 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#4 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-admin/admin.php(224): do_action('settings_page_p...')
#5 /home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-admin/options-general.php(10): require_once('/home/deb38267n...')
#6 {main}
   in <b>/home/deb38267n2/domains/robertvanbregt.nl/public_html/wp/wp-content/plugins/pushover-notifications/includes/admin/admin-pages.php</b> on line <b>280</b><br /></strong>