Granfana Oncall OSS and Zabbix integration

Hi

I need to integrate Grafana Oncall OSS and Zabbix
Both are installed on seperate local virtual machines
Both can ping each other via IP address

I cant get Grafana OSS OnCall to integrate with Local instance of Zabbix. The Dashboard works fine and pulls data via API but i need the OnCall alerting system to work. The heartbeat URL doesn’t work even when using the IP instead of LocalHost.

Thank you