I created the item “net.tcp.service [tcp, 127.0.0.1,3306]” and the trigger

{host: net.tcp.service [tcp, 192.168.0.5,3306] .max (5)}=0

Host 127.0.0.1 is the MySQL database in which Zabbix stores data.

If the connection to the database is lost (the server is working), the server will send a notification about the trigger after the connection is restored.

Solution: cache the data(email, sms, jabber) to whom to send notifications.