Having to hold the shit key to multiple select.

I use Draftsight 2023 Premium on 2 different computers and 2000 Professional on 1 at another workshop's Pc,  If you wish to select more than 1 entity you have to hold the shift key down. The other Pcs you can just click on items to select. It wasn't like this years ago so I am guessing it may be a setting that has been changed by mistake. how do I get it back to how it should be.

Many Thanks 

Ian