Configure Log4Net to enable me to debug issues with a Log4Net Splunk appender?

Can someone clue me in to how I might configure Log4net to help with more verbose debugging?

Currently I have a project where I would like to use a Log4Net appender to log to Splunk.

There exists a NuGet package that seems popular: https://github.com/AlanBarber/log4net.Appender.Splunk

Only there is some problem with the URL and I can't figure out how configure either Log4Net or the appender to help me understand what is wrong with my config.

Here is my config:

<configuration>
    <log4net>
      <appender name="Console" type="log4net.Appender.ConsoleAppender">
        <threshold value="DEBUG" />
        <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="Console Logger: %date %-5level: %message%newline" />
        </layout>
      </appender>
    
      <appender name="Splunk" type="log4net.Appender.Splunk.SplunkHttpEventCollector, log4net.Appender.Splunk">
        <ServerUrl>https://my_trial_cloud_splunk_server_name.cloud.splunk.com:8088/services/collector</ServerUrl>
        <Token>de63d82e-6f5d-4f72-a03c-018d462c30c8</Token>
        <RetriesOnError>10</RetriesOnError>
        <BatchIntevalMs>100</BatchIntevalMs>
        <BatchSizeCount>10</BatchSizeCount>
        <SendMode>Parallel</SendMode>
        <IgnoreCertificateErrors>True</IgnoreCertificateErrors>
        <threshold value="DEBUG" />
        <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="%-5level [%thread]: %message%newline" />
        </layout>
      </appender>
      
      <root>
        <level value="ALL" />
        <appender-ref ref="Console" />
        <appender-ref ref="Splunk" />
      </root>  
      
    </log4net>
<appSettings>
        <add key="log4net.Internal.Debug" value="true"/>
    </appSettings>
</configuration>

I've set the log4net debug to true. Only, even if I have the wrong URL I don't see any log information saying there was trouble with the Splunk endpoint. How do I get more verbose debugging that there is some issue?