Why is my garage door suddenly not operating at all?
Okay, I figured out on my own. I found the user manual for my model (Genie ISD990), and the troubleshooting section says "reset opener - unplug" if status light is blinking (1 blink). I unplugged the power, wait for a few seconds, plug it in again and it works now. Don't know what has caused this. This opener is at least 10 years old, but never had any problems.