If you notice that some of your photos are unexpectedly out of focus, one of the first camera settings to check is AF Point Selection.
The Canon EOS Rebel T7 has 9 autofocus points. When Automatic AF Point Selection is enabled, the camera can choose between all available AF points when focusing. If the camera is accidentally set to Manual AF Point Selection, only one specific AF point may be active. If that point is not positioned over your guests, the camera may focus on the wrong area of the photo.
Turn the camera on and make sure the switch on the lens is set to AF, not MF.
Press the AF Point Selection button on the back of the Canon T7. It is located near the upper-right corner of the camera.
The AF points will appear on the screen and in the viewfinder.
Press the SET button to switch between the center AF point and Automatic AF Point Selection.
When all AF points are displayed, Automatic Selection is active.
Press the shutter button halfway to return to shooting.