Well, if you had any older SketchUp versions and had run them in that same session that you attempted to run a SketchUp installer (either to update your version or trial a newer version,) there would often be leftover webhelper.exe processes still using resources.
We’d see them in the task list of Windows Task Manager. (These are utilities that SketchUp’s various web enabled dialogs use.)
Anyway, these “orphan” processes often interfered with the installers because some newer versions need to update that executable, and Windows won’t allow that if it thinks a program is in use. (Security reasons, etc.)
So, rebooting the computer will clean out memory and unload stuff no longer actually in use.
Going forward, this past 2021.1 release has made the following fix:
- (Win) Fixed a problem to ensure the removal of unused webhelper processes.
The same sort of thing can happen if you have some program or application running that is using the MS C runtime and SketchUp’s installer wants to download and install a newer runtime version from Microsoft.
So generally when installing software, close everything, reboot to clean memory, then run only the installer (“as administrator”) and reboot again afterward.