Hello,
It looks like we have two issues here:
1. Corona Uninstaller does not uninstall the files from C:\Users\Administrator\AppData\Local\Autodesk\3dsMax\2015 - 64bit\ENU\usermacros (maybe it is intentional as these are USERmacros?)
2. After I uninstalled Corona 1.0, manually deleted usermacros, and installed A6, the proxy exporter is greyed out - the file is missing. Conclusion: proxy exporter is not bundled with th A6 installer. You can also check it by unpacking the A6 setup files.
I will look for a proxy exporter that works with A6. Stay tuned. :)