Your are correct. Sounds will not appear because there is NO dll.xml file for V5 in the C:\Users\name\AppData\Roaming\Lockheed Martin\Prepar3D v5 folder.

What you need to do is go to C:\ProgramData\Lockheed Martin\Prepar3D v5 and add the folowing entry to the dll.xml file:
   
   <Launch.Addon>
     <Name>Captain Sim Sound</Name>
     <Disabled>False</Disabled>
     <ManualLoad>False</ManualLoad>
     <Path>Captain_Sim\bin\cs.sound.dll</Path>
   </Launch.Addon>

NOTE: this will probably be your first entry into this file

Be sure to SAVE.

Open up your V5 and clicks are audible along with warning sounds.

Mine works.   And all I did is copy files from V4 to V5.