Not finding the GPS signal
Polar G3/G5 GPS sensor W.I.N.D. and Polar G1 GPS sensor need signals from four different satellites to establish the starting position. Depending on the circumstances these signals should be found within 30 - 60s, sometimes even faster if you have started the G3/G5 or G1 GPS sensor at the same position previously.
The signal is generally found faster if you remain stationary during the search.