
Hey, that sounds frustrating, especially when you're trying to capture those precious moments with your grandkids. Since you've already cleaned the lens and checked the basic settings, let's try a few more things to diagnose the autofocus issue. First off, make sure the switch on your lens is set to AF instead of manual focus, because sometimes that gets bumped accidentally. If that's good, take off the lens and gently clean the metal contacts on both the lens and the camera body with a soft cloth; dust or grime there can mess with communication and cause focusing problems.
Another thing to look at is the autofocus mode on your camera. Switch it to single-point AF and select a focus point right on your subject, which might help if it's struggling with multiple points or low-contrast scenes like indoors with the kids. Also, if you're shooting in low light, the autofocus can have trouble, so try adding more light or using a tripod to steady things. If none of that works, reset the camera to its factory settings through the menu, as that often clears up glitches without losing your photos.
I've had similar issues with my own DSLR, and these steps usually get it back on track. If it persists, it might be worth having a professional look at it, but hopefully this sorts it out for you so you can keep snapping those clear shots.