I manually edited the exe file to point it in the right direction as Prepare3d is on my E drive and fsx is on my C drive which has been deactivated by the migration tool.
There wasn't any need to edit it manually, of course. Our installer correctly set the Path command, and it uses RELATIVE paths, like this:
<Path>fsdreamteam\couatl\couatl.exe</Path>This means "launch the exe starting from the path YOU are running from", with "YOU" means the Prepar3D.EXE itself so, this will work regardless of the path you installed P3D into, and it's entirely independent from FSX, if you have it or not, and where it's installed.
However, if your EXE.XML looks exactly like the one you posted, it's no wonder it doesn't work because, when editing it, you forgot to close the <Launch.Addon> tag. The unclosed tag result in a syntactically incorrect XML file, so P3D will surely ignore that section, if not the whole file.
So, that section should look like this:
<Launch.Addon>
<Name>Couatl</Name>
<Disabled>False</Disabled>
<ManualLoad>False</ManualLoad>
<Path>fsdreamteam\couatl\couatl.exe</Path>
<CommandLine>--mode=prepar3dv2</CommandLine>
</Launch.Addon>
Of course, assuming you still have the XML file header correct, otherwise nothing will work. The easiest solution would be REMOVING the EXE.XML file altogether, and reinstall GSX, so our installer will create a new, correct one, from scratch.
And, as explained several times on the forum, if you use the P3D Migration Tool, you must DISABLE IT when installing and using any of our software, because that tool will confuse any P3D-aware product, making it mistakenly think is running under FSX and this WILL cause all our products to malfunction, because they must be able to recognize P3D.