Flatten command. What am I doing wrong?

I select the elements in the drawing and got to Tools>Flatten. The watch spins for a beat, then nothing. The lines are still individually selectable. I’ve tried not selecting the elements before flattening. I’ve tried the hot key. Nothing. Layers are not locked and have no transforms.I’m using the latest version of SBPro on a Mac.

Hi,Be aware that flatten does not group the element, it simply remove any invisible lines (from cross sketching and such). Basically all the colors that overlaps will be removed to keep only what you see as a selectable element. Regards,Ugo