The button seem active when I select it, but it won't draw.

Any suggestions?

Is Orthogonal Lock (in the Snap toolbar) active?  Orthogonal Lock allows extension in only one axis so when it's on you can't draw Doglegs or other objects that require extension in both axes at once, e.g Rectangle and Circle/Arc.

If these three tools appear greyed out, then Orthogonal Lock is on.  Uncheck it and they'll become active again.

I hope this is helpful.

Kind regards,
Rob Robinson
Stardraw.com