found this on another site, worked for me.
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CK
C675D-S7101 Keyboard replied on March 19, 2017
Found the fix on another forum. It worked beautifully. Delete Synaptics Pointing Device, then reboot.
:"The culprit, as others have discovered, was the (unrequested) installation of Synaptics (Lenovo) pointing device, the icon for which appeared in the toolbox subsequent to the Windows 10 update on 16th March, 2017.
As for getting rid - difficult. Unfortunately it wasn't listed in my favourite uninstaller software, Revo, so I messed about in the registry and Programmes, finally using Windows uninstaller when it appeared there - not under Lenovo, but Synaptics.
So, it had nothing to do with drivers needing to be updated, on the contrary, it must have been Synaptics own driver/s interfering. Incidentally, though I don't think it is really relevant, the only keys which stopped functioning were digits 1 to 4, and the spacebar. The Keypad wasn't affected."
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