Thank You cery much TIG.
Kaspersky setting is so complex.
Happily I have found that Application Control has had a control on blocking Sketchup functions.
Bizarre enough Sketchup.exe has been fully allowed.
Finally I have removed all Sketchup presence from Kadpersky list and activated App Control within Kaspersky and...I think I have managed to fix the mysterious blocking.
Once more thank you for your taking precious time dropping a line here.
My best regards.