"Live Track" is a special feature for following someone (or self) online, so it looks like it is not what you meant. But anyway, since the GPS on your display is not locked, it means the watch cannot get your position, so tracking or recording the path is not possible.
BTW, I had GPS problems today too - it took my watch almost half an hour to get the position. My EPO file is up-to-date, so I do not know what was the reason. Perhaps we got a faulty EPO fix.
As I wrote above, I suspect there migh have been some corrupted EPO served to our watches today. Connect to a computer with Garmin Express over the USB cable, and check for updates - it will refresh the EPO file.
If it happens again, and you cannot get lock on the GPS, make sure your phone has data connection (assuming you have one with you while running), and that the Garmin Connect app is running and is connected to the watch. If everything looks all right, but still no GPS signal after several minutes, try powercycling the watch.
