When users attempts to view virtual machine logs via the Object Browser in the VMware Aria Operations user interface, the logs fail to display
Aria Operations 8.x
This issue occurs when the Log Insight Agent or syslogd is not present in any virtual machine.
To resolve this issue,
Ensure that the integration between Aria Operations and Aria Operations for Logs are done.
https://techdocs.broadcom.com/us/en/vmware-cis/aria/aria-operations/8-18/vmware-aria-operations-configuration-guide-8-18/log-analysis-with-vmware-aria-operations-for-logs/configuring-aria-operations-and-aria-operations-for-logs.html
Install and configure the Log Insight Agent or syslogd on each virtual machine.
Refer below document on how to install VMware Aria Operations for Logs Agents
https://techdocs.broadcom.com/us/en/vmware-cis/aria/aria-operations-for-logs/8-18/administering-vmware-aria-operations-for-logs-agents-8-18/installing-vrealize-log-insight-agents.html