Smart track faulty

The Smart Track feature on my rhino 5 appears to have stopped working. Any ideas?

Afraid to ask the obvious here, but is it turned on?
Windows or Mac?
In Windows it can be toggled in the status bar or with the command SmartTrack.

Thanks Mitch,
Yes, switched on. Has suddenly stopped working.

OK, odd… Tried a restart of Rhino and/or the computer? Do you have the latest version of Rhino installed? That’s all I can think of for the moment. --Mitch

Got it sussed.
All it was is that the Smart track only tracks from a point if that snap is turned on. ie, will not track from the end of a curve if end snap is disabled.
So simple!!!???