A frequent hotspot for leaks are where the roofline hits a siding wall. No matter how close the gutter is to the wall there is always a gap that water can squeeze into. Over time the water can find weaknesses or small areas to make it through. This can cause leaks and sheeting rot over a lengthy period of time. A kick-out flashing will remedy your leak issue.
Remove a couple pieces of siding where the roofline meets the wall. The kickoff flashing will be custom fabricated out of aluminum to match the siding color (or roof color). This will be one continuous piece designed to flow water into the gutter. The flashing will be taped underneath the siding and will be installed under the shingles.
If this spot is above a window, it’s often mistaken as a window leak when really the window leak is a symptom of not having a kickoff flashing in place.