The modify installation is showing all the extensions as installed.
TC8 has been installed on a clean image on a different PC and is working as expected with the AUT. Its identifying all the objects and they have a little .NET icon. The .NET extension is also showing in the "install extension" list of extensions.
This means its an issue with the TC install on the PC that I am using or the PC itself. We are going to try upgrading another PC from TC 7.52 to 8 and see if it encounters the same problem. Then a manual un-install/install on the PC I use.
Will let you know how I get on.