Why was not Putin invited to the D-Day ceremonies?

The Russian president is the great absent of the Normandy landings commemorations of June 6, 1944, June 5 and 6 in England and France.
The leaders of fifteen countries were gathered Wednesday in Portsmouth, to kick off the commemorations of the D-Day in Normandy on June 6, 1944. Before the photographers, the heads of state representing the Allied powers of the Second World War took the pose: Theresa May and Elizabeth II for England, Donald Trump for the United States, Emmanuel Macron for France and ... nobody for the Soviet Union. Russian President Vladimir Putin has not been invited. Neither in England nor in France, where the commemoration ceremonies continue on June 6th.....