silverheels wrote on Jul 25^th, 2019 at 9:10pm:

All I did was change the volume on a number of the sounds and that seems to have worked.

Let's do not mixup NO SOUND and LOW VOLUME sound issues as they are totally different.
The LOW VOLUME is not even an issue. Just set any volume in the ...P3D4v4\Captain_Sim\757-III\sound.ini.
If you don't like some sound itself, just replace a WAV file. It's an open source thing so any user can do whatever makes him happy.

Now back to the topic.
The NO SOUND issue caused by your AV which blocking our installer from writing into the DLL.XML file. This may help: https://www.captainsim.org/forum/csf.pl?num=1554738484

If it doesnt,
- Add an AV exclusion or turn it off
- Download https://www.captainsim.com/tools/dll-xml-cs-sound-fix.exe
- Run the exe.

If still no joy,
Open %APPDATA%\Lockheed Martin\Prepar3D v4\dll.xml

And MANUALLY add the following:
<Launch.Addon>
    <Name>Captain Sim Sound</Name>
    <Disabled>False</Disabled>
    <ManualLoad>False</ManualLoad>
    <Path>Captain_Sim\bin\cs.sound.dll</Path>
</Launch.Addon>