the roof deck was not installed correctly. It's too close to the facia board. The lower edge of the roof should extend a little further so that the water will go to the gutter. This one is too close so when the shingle was installed last time the guy tried to extended down. However this made things even worse because the lower edge of the shingles is loose that allows water to go through it.
The second mistake was the drip edge was not installed or not installed correctly.
At this moment the the lowest row of roof plywood deck is probable gone.
You can have the option to either replace the lower part of the roof (deck and shingles) or the whole side. Some rafters may need reinforced (I don't think you have to replace them) and all the facia boards need replacement.
