If your Garage Door faces South and the door will not go down. It may be that your Safety Sensor is being blinded by the light of the sun. This was happening to our garage door. After trying lots of tricks posted from Youtubers and other folks. I learned a few things:
1. South facing garage doors can be blinded causing the door to not go down. (it essentially thinks something is blocking the door and it will go up to not cause harm.
2. Liftmaster Safety Sensors are prone to this issue.
3. You can try a toilet paper roll taped to the safety sensor and it may or may not work
4. If it continues and your opener motor light blinks 10 times it's the sensor being blinded.
5. Liftmaster acknowledge the problem in 2007 and developed a corrugated plastic shield Part# 41B873; that you can buy to try and solve your problem. This may work better than toilet tissue roll, but maybe not. (Our's is working at the moment.
5. The Installation instructions are really really bad; and not really clear.
This video will try and show you how we folded up the little box and installed. It's currently working so Yay.