ok thanks for the suggestions so far.
I rebooted the Synology. Then a TimeMachine folder appeared on, as if by magic, on the desktop. I clicked on it
and all the sparsebundle with all folders insider was fully accessible
But now there is a another problem. When I use Finder > Go
"Diskstation" has disappeared? Where has this gone to?
(ps: Who said Synology devices were reliable...)