The focus red frame of Canon 5d3 camera disappeared. How to set it?

The specific operation steps are as follows:

1. First, press the button to adjust the focus mode on the front lens of the camera to ".

AF mode "(autofocus mode), as shown in the figure below, and then go to the next step.

2. Secondly, use the "autofocus mode" of the lens to shoot the double focus of the subject. After confirming that the focus is correct, switch the focus mode of the lens to "MF mode" again, as shown in the figure below, and then proceed to the next step.

3. Next, click the "autofocus" selection button at the position shown in the figure below, as shown in the figure below, and then go to the next step.

4. Then, use the turntable to adjust the lens distance, as shown in the figure below, and then proceed to the next step.

Finally, aim the camera at the screen, and the red light is the focus of choice. After the camera is successfully focused, it will make a "drip" sound, and then press the shutter button completely to complete the shooting, as shown in the following figure. In this way, the problem is solved.