***Ensure you are using a standard USB adapter Plug-In and not a "Fast Charging" Adapter, as the device will not charge using the higher output "Fast Charging" adapters that are becoming more widely used by mobile phone devices.***
Give your MicroSim sensor a well-deserved break for 2 full days and nights. Let it fully drain its battery and then plug it back in, to recharge. To expedite draining the battery, you can keep the sensor moving by keeping it in you pocket throughout the day, and double tapping the arrows to wake it up. Once it has drained and stayed dead for 24hrs, put it back on standard USB power: 5V 1a and charge it back up for 1hr...Since the electronics and the battery both start at a state of zero charge when the board "wakes back up" they sync back up and the battery will take on more "juice" and last much longer. This should do the trick and get it back to its usual self. We also suggest you updating the devices firmware to the latest version, see how to do that here -> UPDATE FIRMWARE
And if it still doesn't work, don't worry, we've got your back. Just fill out a Warranty Claim Ticket requesting a replacement sensor, but only after you've given the above method a try. Then we'll sound the alarms in the returns department and let them know that it's time to get back to work. Because we're not giving up until your MicroSim device is functioning like a champ.