wireless keyboard not working at login

I have a iMac 2015. My mac was in sleep mode, and I came back this morning to login. But the wireless keyboard is not working. Wireless mouse works fine. I cannot type in password at login. I changed the batteries. It has power and the caps lock light stays on when I press it which I believe means it has a connection to computer. I have no other keyboard so no way to login and troubleshoot. I did have the same problem last week and it seemed to fix it self after several on/off power to keyboard and long presses of power button to try and reset it. This time thought nothing seems to work. Any ideas?