My IMac wireless keyboard stopped working

My iMac wireless keyboard stopped working so I am unable to type. It isn’t dead because it’s able to turn on but for some reason it doesn’t let me type. I replaced the batteries but it still doesn’t work and the green circle on the right top corner blinks two times then pauses and repeats for about a minute. AND I’m on my computers lockscreen so I can’t get into my computer unless I can type in my password.