How to get NLog working outside VS Development Environment - vb.net

Question

I have a bit of a conundrum here. For some reason my Nlog implementation will no longer work from an installed executable, works perfectly well from the VS2013 development environment, but nada from the installed executable.
DevEnv is VB.NET.
My first port of call in terms of diagnostics was to add:
internalLogFile="c:\log.txt" internalLogLevel="Trace"
to the nlog.config file, but this suffers from the same problem, (works in devenv but not from executable). My log files get written to a folder structure in the CommomApplicationData folder,
d:\programdata\CompanyName\AppName\Logs
nlog.config is installed in and read from:
d:\programdata\CompanyName\AppName\QueryConfig
the reason for this is that our corporate IT security prohibits writes to the C: drive (other than via authorised installs), and I have a variable in the nlog.config file 'LogId', that needs to be updated from the app. Here is my nlog.config file:
<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" autoReload="true"
internalLogFile="c:\log.txt" internalLogLevel="Trace">
<variable name="companyName" value="Company Name"/>
<variable name="logFolder" value="${specialfolder:folder=CommonApplicationData}/${companyName}/AppName/Logs/"/>
<variable name="startDelim" value="["/>
<variable name="endDelim" value="]"/>
<variable name="filename" value="${date:format=yyyy-MM-dd}_${gdc:item=appName}.log"/>
<variable name="fieldDelim" value="|"/>
<variable name="logId" value="1"/>
<variable name="headerLayout" value="Application Name: ${processname} File Version: ${gdc:item=fileVersion} Released: ${gdc:item=releaseDate} User: ${windows-identity}" />
<variable name="normalLayout" value="${gdc:item=logId}${fieldDelim}${date:format=HH\:mm\:ss}${fieldDelim}${windows-identity}${fieldDelim}${level}${fieldDelim}${message}${exception:format=tostring}" />
<variable name="traceLayout" value="${gdc:item=logId}${fieldDelim}${date:format=HH\:mm\:ss}${fieldDelim}${windows-identity}${fieldDelim}${level}${fieldDelim}${message}${exception:format=tostring}"/>
<targets async="true">
<target name="fileHeader"
xsi:type="File"
fileName="${logFolder}${filename}"
layout="${headerLayout}"/>
<target name="normal"
xsi:type="File"
fileName="${logFolder}${filename}"
layout="${normalLayout}"/>
</targets>
<rules>
<logger name="HeaderLogger" minlevel="Info" writeTo="fileHeader" final="true"/>
<logger name="*" minlevel="Trace" writeTo="normal" />
</rules>
</nlog>
This Nlog implementation has worked fine for the last 5 years the only difference is the diversion of the nlog.config and log file destination to the CommonApplicationData folder. Testing of a windows service app that uses the same logging implementation works fine from the same machine, the only differences are that it runs as a service under the system account and does not require write access to the Nlog.config file, as a consequence of which nlog.config resides in the application folder on the C: drive. Hope somebody has some input into this because its driving me crazy...!
Edit: I should add, that I have full Admin rights on this machine under my corporate user ID, however normal users won't.
Kind Regards
Paul J.
EDITED 2018-08-14
OK, so... as suggested have altered the relevant code to launch internal logging programmatically to write to log.txt in c:\temp. Curiously, this appears to work to an extent. However content of the output is rather sparse when compared to internal log output when launched via the config file. As expected, the actual application logging remains inactive.
Sample log from log.txt when internal logging implemented programmatically:
2018-08-13 15:21:34.9302 Debug Targets for HeaderLogger by level:
2018-08-13 15:21:34.9302 Debug Trace =>
2018-08-13 15:21:34.9302 Debug Debug =>
2018-08-13 15:21:34.9302 Debug Info =>
2018-08-13 15:21:34.9412 Debug Warn =>
2018-08-13 15:21:34.9412 Debug Error =>
2018-08-13 15:21:34.9412 Debug Fatal =>
2018-08-13 15:21:37.0902 Debug Targets for HeaderLogger by level:
2018-08-13 15:21:37.0902 Debug Trace =>
2018-08-13 15:21:37.0902 Debug Debug =>
2018-08-13 15:21:37.0932 Debug Info =>
2018-08-13 15:21:37.0932 Debug Warn =>
2018-08-13 15:21:37.0932 Debug Error =>
2018-08-13 15:21:37.0932 Debug Fatal =>
2018-08-13 15:21:39.1012 Trace LogFactory.Flush(00:00:15)
...
finally when the app is closed down the log finishes with:
2018-08-13 15:35:56.9262 Info Shutting down logging...
2018-08-13 15:35:56.9262 Info Logger has been shut down.
Kind Regards
Paul.