1, the lens is not installed properly, and the bayonet and lens are not closely matched. The solution is to take the lens down and put it back on.
2. The contrast of the subject is not enough. Although SLR (Sony is a single lens with fixed mirror and half lens technology) focuses in phase difference, it still needs the subject to have a certain contrast light, and the contrast is not obvious (for example, focusing on a pure white wall), so you can't press the shutter. The solution is to manually change the focus or focus.
3, beyond the macro focus of the lens, press the shutter too close. Lens macro is innate and has no solution. It can only be solved by widening the shooting distance.
4, the camera's focusing ability, such as dark light environment, some cameras can reach -3EV or even -5EV, and some can't, because the dark light focusing ability is insufficient, the shutter can't be pressed. The solution is to focus manually.