For TheSky error with PHD you need to run TheSky one-time-only “As Administrator” so that TheSky’s automation interface is registered with Windows.
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Assuming the above steps fix the problem reboot the computer and carry out a manual “check for Windows updates” from the Windows Settings tool to ensure the Windows Update service is working properly.
That was it! Discovered it myself a long time ago by trial and error, which is why it was both familiar and not immediately to mind.
My TCS has had Windows Update switched off in a hard-wired registry setting, so WU never works even when explicitly asked for. That way a working system doesn’t get munged by Microsoft into a non-working one. If it aint broke, don’t fix it. I am not concerned with security vulnerabilities as it is a dedicated system and heavily protected with multiple levels of firewalls. A simple web search will tell you how to follow suit should you wish.
Paul