Symptoms

If there are events missing on Dashboards (lines, columns and pie charts are metrics widgets, tables are event widgets), the issue is most likely in Machine Agent or in its settings. 

Solution

Machine Agent has to be started on every application server (because events can be sent through any server on which Datavard Insights collector is running) and every Machine Agent has to have HTTP Listener configured correctly.

If both of these criteria are met, the connection status in /DVD/APPD_STATUS will be green.

If the status is not green, one or both of these criteria is not met.

If despite all this no custom events are displayed under an application or a tier, it is an issue with a Unique host ID. It is caused by ABAP Agent or HTTP SDK sometimes returning a different hostname (used as a Unique host ID) than is returned by Machine Agent and they cannot be paired automatically.