If an increased amount of humidity enters the holder, a bridging of the pin contacts for the pc-link can become an issue. This effect might occur if you take the MACRO from its holder and put it back whilst it is raining heavily.
Solution:
Take the MACRO from its holder and dry the contact points of both MACRO and holder. To avoid a switch into the pc-link mode, please start the stopwatch. If the stopwatch is active the pc-link mode will be disabled. How to start the stopwatch? You can read it here: 4. Why isn’t there any data saved on the MACRO after a bike tour?