300D Electrical Sliding Roof

My sliding roof would not open with the electrical switch and I
suspected my roof rails needed lubrication, so I opened the roof
manually, applied approved Mercedes-Benz lubricant, then closed the
roof with the electrical switch.  It operated normally.  However, the
roof will not open electrically.  It will close fine, but not open.

Any information about why the roof moves one way but not the other
will be appreciated.