I’ve seen this intermittently on several computers, particularly ones not running in English. I’ve not been able to reproduce the problem myself - except this:
There’s a setting in the installer that disables the check-for-updates system. You get here by clicking the gear icon on the first page:
If the user clears the highlighted checkbox, then they get the symptom you describe. The setting is a machine-wide setting, which is why the checkbox is grayed out in Rhino.
See if uninstalling and then reinstalling with the checkbox checked fixes the problem.