Macbook does not recognize the projector

macbook_projector_fix

Normal way: 
- Click on the Apple Menu in the top left corner of your screen
- Select System Preferences from the drop-down menu
- Select the Displays icon
- When the Displays window appears, select the Arrangement tab within the menu bar
- Check the Mirror Displays box in the lower left-hand corner of the window (Note: After checking this box, please wait several seconds. Once the displays are mirrored, you should see the same image on both your projector and computer.)

First, reset what is called the Power Management Unit (PMU) using these steps:
- Shut down the computer.
- Connect it to AC power.
- Press the left shift + command + option + power button.

Second, reset the Parameter RAM (PRAM) on the computer using these steps:
- Shut down the computer.
- Press the power button to turn on the computer.
- Immediately, before the gray screen appears, press and hold command + option + P + R. Hold the keys down until the machine restarts and you hear the second startup sound.