Has anyone experienced a failure with the e53's auto-dimming interior rear view mirror?

Mine does not appear to be responding to light input and before I go to too much effort trouble shooting in what could very well be the wrong direction, thought I would ask the forum.

Fuse (number 6 in the glovebox fuse box) is ok.

No other electric problems with the vehicle.

Searched the forum with no matching result.

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Cheers,

Anthony