By default, new installations of the portal have Portal Agent tracing turned off. To add it in, replace the <system.diagnostics> .... </system.diagnostics> section with the content below.

<system.diagnostics>
<sharedListeners>
<add initializeData="Passageways Portal Agent" name="CoreServicesTrace" traceOutputOptions="None" type="System.Diagnostics.EventLogTraceListener" />
</sharedListeners>
<sources>
<source name="System.ServiceModel" switchValue="Information" propagateActivity="true">
<listeners>
<add name="CoreServicesTrace" />
</listeners>
</source>
<source name="Passageways.Portal.Services" switchValue="Information">
<listeners>
<add name="CoreServicesTrace" />
</listeners>
</source>
</sources>
<trace autoflush="true" />
</system.diagnostics>

After adding the above, restart the Portal Agent service.

Portal Agent issues will show up in the Event Viewer.