I place my device on the charger or try to start the WIFI with one mag swipe, but nothing happens.

Make sure your device is sufficiently charged. If the blue LED on the charger is still on, wait till it goes off, indicating that the device is now fully charged and try again.

If the device is still in logging mode (recording), you will need to stop the logging mode via 2 mag swipes before you can activate the WIFI mode.