The Shape Builder tool is not working

[Dulce]

Hello, I am new to Illustrator so I am taking an online course. However, when I went to use the Shape Builder tool, according to my teacher there should be a + sign next to the cursor, but in my Illustrator there is a nill sign, and the tool doesn't seem to work. Can anybody help me find out what's wrong? Thanks!

[Monika Gause]

Did you select anything?

[federico platon]

Select the objects first, or if you have already selected that tool Hold  Cmd/Ctrl to drag around the objects you will use, or click while holding Cmd/Ctrl+Shift each of them. (Alternatively slect first the Selection tool (black arrow) and select them (hold Shift to add to the selection).

Well now you have objects selected and the Shape Builder Tool. it must look like a black arrow (triangle) point, and on its base should show up a small + sign, if instead you are seeing two lines crossing, press to release the Caps Lock key of your kayboard!

A Nil sign an slashed O, o well, that's beacause you need to FIRST select the objects you will use with the Shape Builder Tool !

[Monika Gause]

There are videos in the Help section https://helpx.adobe.com/illustrator/how-to/shapes-basics.html