Deleted files do not end up in trash bin

When I delete a file, it does not end up in the trash bin but it is directly deleted from the computer. I get a warning message: 'file will be immediately deleted. Do you want to proceed'. Whe choosing yes, the file is deleted - the trash bin remains empty. When choosing no, the file just stays where it is.

This problem suddenly occured a few days ago, I don't understand

Thank,

Paul Menken
NL