How do i fix my leak in conservatory on wood joint?

i have just had a conservatory built on the side of my kitchen. The roof on my kitchen is sloped down, therefore i have had to have an internal gutter across the bottom of roof over my kitchen door. After approx one month i have had a leak when i have taken the plastic boxing off to see where the leak is coming from it appears to be dripping down the corner of the wood (where the internal guttering is boxed around). Have you got any ideas