Excuse me, Canon 600D can only focus when taking photos in the dark, and it is difficult to press the shutter. Why is the red light always on? How to adjust it?

Canon 600D is an entry-level SLR camera. Taking pictures in a dark place may be that the camera can't sense the focus and the shutter can't be pressed. The red light is always on, which is why it can't sense the focus. You can choose other focusing modes to try. If not, you can only focus manually.

I hope I can help you.