EDIT -
Nevermind. After all that, I find that it's a known issue with 5.44.6575. Wasted my time again.
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Windows 10 x64, all updates. CCleaner 5.44.6575. The option to keep files less than 24 hours old is disabled.
Using right-click menu on Recycle Bin, if I choose "Run CCleaner", the RB is not emptied.
If instead I choose "Open CCleaner", then within that click on lower-right button "Run CCleaner", the RB is emptied.
==> Does this happen for other people? Or does the right-click "Run CCleaner" work OK for you?
I have tried deleting / restoring the Recycle Bin in case it was corrupted. No change in symptoms.
[Speculation: This is a fairly new problem and may be due to a Windows update. When I actually open CCleaner and then tell it to clean (the second path above), it always asks if I want to close MS Edge, even when I have just rebooted. I have to tell CC to proceed anyway. Is it possible that in the more automated right-click menu "Run CCLeaner" this (bogus?) question about MS Edge is preventing CC from doing anything?]