Garage door stopping while closing
 

One sensor has a red light; the other is not lit...should it be green?

Usually they should both be green. Sounds like they aren't lined up.

Do you have a painted floor
 

Sometimes the glossy finishes on painted floors can interfere with the door closing. The sunlight reflection doesn’t permit the door closure because of the sensors. This is particularly true of garages that open to the afternoon Westward sun. Just hold the button down on your wall mount switch or shadow the appropriate sensor while attempting to close.

The color of the LED depends on the make of your garage door opener. If you have a MVP opener, one of the sensors has the RED light the other does not have any light. With the garage door UP you can block the beam and the RED light will go out and come back on when to remove the block. On the back of the MVP garage door opener there are 2 LEDs one RED and one GREEN. Normal operation both are off. If one or both are flashing they are displaying a code for a problem. Your instruction manual has the listing of the codes. I believe I have this downloaded if you cannot find yours.
Also, if the door is up and starts down and then goes back up you probably have a loose wire at the connection of the sensor to the cable going to the opener, I just had to fix one like that last week.
Hope this helps.

When the sun is at a certain angle, I need to stand so that I cast a shadow on the sensor and use the clicker to close the door. It rarely happens because I typically use the overhead screen door (which doesn’t have sensors) instead of the actual garage door.

better call a Pro ... if your asking these questions in this forum , you may be in over your head...

Garage door sensors.
 

I just had this happen to my garage door, pres the opener, garage door cones down about a foot and goes back up. Checked sensors, and red light was out on the one sensor, so tried to re align them, with no success, Went on Amazon to find a pair of sensors, but no luck. Went on E-Bay, and found them right away. Ordered them, right around $60.00, got them in 3 days, took them out to the garage and installed them in about 10 minutes, very easy install, don't have to turn of electricity, low voltage wires. Red light came on immediately, I went and pushed garage door opener, and all worked perfectely.

Had the same problem and got tired of it. Finally disconnected one side and wired them together on one side and duct taped together with sensor facing each other. Problem solved forever. Never had a need to have the door reverse itself because something was in the way. If I still had young children that would be a different story

Sun was blocking the beam. I taped a plastic shade to the front side of the exposed sensor which solved the issue. 😎😍

Playing card
 

Can tape a playing card ( from a deck of cards) on the sun side of the sensor so it sticks out and blocks the sun if it is a sun issue. 2 cards, 2 pieces of tap, 2 minutes too do. Good luck.

I just installed a Chamberlin GDO for a neighbor. One is red, one is green IF they are aligned. Also, directions warned to keep green light out of heavy direct sunlight. Also needed to "set" the limits by using the up/down button on ceiling unit before use.

If your problem is a misalignment of the sensors, usually resulting from one being "bumped", buy a cheap laser pointer. Set it on top of the sending sensor, tape it in place if necessary, and use the laser beam while bending the brackets to bring the infrared beam in line with the receiving sensor.

If your problem is sunshine falling on the receiving sensor, the best solution is to glue a short length of PVC pipe on that sensor. I found that a 2" length of PVC was enough. You may have to realign the sending sensor so that the infrared beam hits the small opening of the PVC.

Sometimes the setting sun hits one of my sensors and stops the door from going down. I have to block the sun's rays to get it to finish the cycle.

Do a search on You Tube.

I have a Genie and had adjustment issues.
I called their 800 number, and all my questions were answered on the phone.
Really nice people.