Have you ensured that the channel parameters of the two devices match? Also, are you certain that the Geonaute product is ANT+? The link you provided makes no indication that it is or not.
Turns out this speed and cadence sensor looks to have the pairing bit set which of course means most display units fail to find it when doing a wildcard search. If the display allows a manual setup then if you know the Device ID you can set it up manualy and it then looks to work.