Steps to reproduce:

Zabbix Server and Agent 2 version is 5.0.7.

Tried the steps found in https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/templates/app/certificate_agent2/README.md?at=refs%2Fheads%2Frelease%2F5.0

1. Setup and configure zabbix-agent2 with the WebCertificate plugin. According to the documentation the plugin is available out of the box in Zabbix Agent 2
2. Test availability: zabbix_get -s <zabbix_agent_addr> -k web.certificate.get[<website_DNS_name>]
3. Create a host for the TLS/SSL certificate with Zabbix agent interface.
4. Link the template to the host.
5. Customize the value of {$CERT.WEBSITE.HOSTNAME} macro.

Result:

No web cert latest data from host

logfile in zabbix server shows the following:

web.certificate.get[{$CERT.WEBSITE.HOSTNAME},{$CERT.WEBSITE.PORT},{$CERT.WEBSITE.IP}]" became not supported: Unknown metric web.certificate.get

Step 2 zabbix_get also returned ZBX_NOTSUPPORTED: Unknown metric web.certificate.get

Expected:
should be able to get web cert information