Your garage door not working correctly can be traced back to many different causes. This video explains how to diagnose and possibly fix simple garage door problems in five steps.
The first step is to check if your opener is plugged into the power. Sometimes this can get unplugged by mistake. Then check if the sensor is obstructed or misaligned.
You can clean or move it around to possibly correct an unworking sensor. After this, check to see if the garage door is off track. An angled door means you could possibly have a snapped cable, which means you will need to find help from a professional due to the nature of this repair. Then check if the springs are broken by looking at the top of the door and examining the state of the springs. Lastly, check if the trolley is disconnected. This can happen either intentionally or accidently by pulling on the red rope. You can connect it by putting it back in position and pressing the button.
Remember to be extra cautious when it comes to DIY garage door repairs and to know when to call a professional.