where did the icon to open a new tab go?

There used to be a '+' symbol next to my last tab, to open a new tab. I just noticed that is gone. Where did it go? After looking up how to open a new tab, I see that I should get the option if I right click on the empty space next to the last tab. This gets me multiple options, but not the open a new tab option. I also see that clicking the middle mouse button will open a new tab, but my track pad does not have a middle button. Please help.