Digital camera won't focus
I see your camera has a focus area. If you have a subject with enough contrasting parts in this area, the focusing should work fine.
You must know that not every subject can be focused on as quick or as good as you would like. If there are little contrasting lines in the subject, or when it is getting dark or there are dark and light parts in the focus area, that don't belong together, every camera can have problems to focus correct. Changing the ISO settings won't change anything for the auto focus.
But special when you try to shoot in almost dark places, you camera will have lots of work to focus and in most cases it won't work at all.
You could try to place an object with light and dark lines, on the same distance as the object you want to picture. Then by pressing the shutter half, when focusing on the object with much contrast, you can look if the camera can focus. If it is in focus, keep the shutter pressed half way down, while moving to the object you want to shoot a picture of. Once you have every thing in the frame as you want it, press the shutter complete.