So a little back to basics perhaps ?
What ISO is the camera set to ? Set it to 1600 on the back menu to help have a known faster shutter speed to identify the cause of the focus issue.
OK, next set the camera on Av mode (aperture value). Now rotate the rotary dial right behind the shutter release to set the aperture value to the lowest available for the lens you have (3.5-4 if you have a typical zoom lens). Set the lens to its widest angle/shortest focal length.
Take a piece of newsprint or a black and white printed page with good size text on it (about 1/2" high test would be ideal) and fasten it to something so that you can put the camera on a tripod and have the back of the camera parallel to the page. The text on the page should fill the frame.
Make sure that the switch on the lens is set to AF, not MF. Go to the menu on the back of the camera, first page, AF Mode: set it to "one shot". Below that "metering Mode" pick the top of the 3 options (square with an ellipse with a dot in the center). Directly below that, ISO speed = 1600 The very top item "quality" should be set to L with a curve to the left of it.
Last check, for the focal point, press the button top right of the camera back (on top of the camera it should show a cross with all of the available focal points). While holding down the botton, rotate the wheel behind the shutter release until the focal point directly in the center of the viewfinder is illuminated (just 1 not all of them and right in the center).
Now fix the camera to the tripod, press the shutter release half way and see if the text is sharp in the optical viewfinder. If it is, press the shutter release in all the way and take a picture. If you are too close to the sheet of paper the camera may not be able to focus or if it is dark it may try to use the AF illuminator which may not focus accurately. So do your test in daylight, possibly not in direct sunlight since the contrast would be severe.
If the image is sharp in the optical viewfinder, it should be sharp in the image file. Sometimes with a wide angle lens it is very difficult to judge the focal point, so zoom in and then the depth of field will be reduced and the focus may be more exact. Even more important to use the tripod with a longer focal length since unless the exposure time is shorter, you are more likely to get blur from camera movement.
If none of that works, then it suggests that there is some problem with the optical phase shift of the focusing system and may need repair. That may render the camera a candidate for astrophotography or similar pursuits where the focus is always at infinity....
