There may be a connection issue indicated by a green light that will blink 4-5 times. Connection issues can happen when a cartridge leaks or you are using an irregular-sized cartridge. If the issue is a leak, turn off your battery and take a Q-tip dipped in rubbing alcohol and clean where the battery and cartridge meet. Make sure to dry them before screwing them back together.
Another reason your battery may be flashing is because it may be dead and needs to be charged.