Pack installer update error (vendors.idx)

I get the followong error when uVision V5.31.0.0 starts:
   Cannot download vendor lookup file https://www.keil.com/pack/vendors.idx - Continue check for update with previous copy
   Check for updates error: Cannot download www.keil.com/.../vendors.idx, Cannot modify read-only attribute.

This stops further work. Any clues?

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