I have solved this by myself. I installed another piece of software and Just like NIK 9 it would install and then not run. Unlike NIK 9 it was kind enough to give me an error in Windows Application Event Log which pointed to a faulting DLL file. I realised that this was related to Microsoft Visual C++ so I installed the latest version of their Visual C++ 2015-2022 Redistributable Somewhere between my original install of Nik 9 C++ must have got corrupted. I suggested that DxO might want to add this to their FAQ and/or support crib sheet. Hope this might help someone else faced with this problem. I remain very unhappy with DxO’s support, takes ages and, beyond their initial support replies doesn’t give any constructive advise. Their “developers” only made one suggestion and that was to delete the license file and re-install. I knew that wasn’t going to fix it as the progam didn’t even get as far as checking for a license file.