Ctrl+Click is net highlight, not selection. It looks the same but it’s sticky, so you can keep a net of interest highlighted while using other tools.
Once you’ve net highlighted something, you can unhighlight it by ctrl+clicking in empty space. You can also use ~ to clear all net highlighting, or ctrl+` to toggle highlighting.
As @jmk says, shift+click to add to your selection and ctrl+shift+click to remove.