Many Riders start their new season with new batteries regardless of the current battery level. With the magnets now optional when riding, a problem has been arising with some people forgetting that the magnet (supplied) is still used to switch the cranks from "computer" mode to operating mode.
When you install new batteries, in cranks numbered below about 3200, you will see a flashing light that continues for some time. That indicates that the batteries are installed and the InfoCrank® is now in computer mode. Waving a magnet across the rear RF cover will switch the mode to operating. Your cranks are ready to go now. For precautionary reasons, before first use, do a zeroing on your head unit - often called calibration.
For cranks numbered after about 3200, you will not see a continuous light - if you were quick you will have noticed one flash as the batteries made contact. Your cranks should be ready to go as soon as the battery cover is tightened. If they will not pair immediately with your head unit or the VINC app, then wave a magnet across the RF cover.
Remember to use SR44 batteries. Verve's preferred battery is the Renata which is available from Verve. However, many other brands are quite accessible in shops locally. Always buy from a large vendor who is likely to have good turn over. You don't want batteries that were manufactured years ago and have been sitting on a shelf losing power for ages.