FAST FLASHING, NON-STOP
This is a mode called Boot Loader. If the crank is left in Boot Loader mode, the batteries will drain fast, the head unit will not connect and power will not be recorded. Boot Loader mode is used in firmware updates, and in some cranks, turns on when the cover is tightened down on powered batteries. If your crank lights only flash once, you do not need the magnet to get them out of BootLoader as they are already into Operating mode automatically.
To turn Boot Loader mode off (when lights are flashing) and switch InfoCrank into Normal Operating mode, simply pass a magnet over the transmitter (Radio Frequency cover) on the back of your InfoCrank arm. This is only necessary in cranks where the green light flashes multiple times when batteries are changed.
SOLID LIGHT
If the crank is showing a solid light there you may need to:
1. Check battery level by using the free VINC App or by following the steps in the General Diagnostics Guide. Low battery levels can cause a solid green light.
2. Remove and replace the cover, and follow the steps above to turn Boot Loader mode off (in cranks where the lights blink) and switch InfoCrank into Normal Operating mode.
http://support.vervecycling.com/support/solutions/folders/1000224997