If you are upgrading from Notes 8.0.2 to 8.5.2, and had a hotfix installed on your 8.0.2 installation it is possible that the 8.5.2 installer will not install the latest version of rcplauncher.exe, causing the upgraded client to be unable to launch, from the technote:
“If the original Modified date of rcplauncher.exe is changed, a newer one will not be copied to disk when a hotfixed Notes 8.0.2 client is upgraded to 8.5.2. As a result, errors may occur during the upgrade and then afterward the client will not launch.â€
The technote covers other causes of the issue:
“Products other than Notes installers, such as a backup and restore program , may copy or move files around on end-user machines. This could result in rcplauncher.exe having a different Created or Modified date stamp.â€
There is a transform file available for download in the technote with deployment instructions to avoid this issue. The technote is worth taking a look if you are upgrading 8.0.2 to 8.5.2.
Clean installs of 8.5.2 are not affected by this issue, upgrades only.