I did something or change the setting somehow and how lines are selected within a drawing. I was able to select a group of Lines/entities within my Cad Drawing and by holding down the Shift button I could add to the existing selection, even if the same lines are part of that second selection box.

Now if I select a group of lines and by selecting additional lines, the ones that were selected now become unselected. 

I would like the current lines selected stay select and when adding additional lines if the window includes already selected lines or entities that they stay selected.

If anyone has advise please let me know.

Where are these setting at and what should they be?