Roof Leaking at Step Flashing

I have a roof leaking at the step flashing, where an upper-level wall/siding intersects with a lower level roofline (garage roof). The siding was replaced 2 years ago and I can see that they used nails to attach the j-channel at the bottom of the wall along the roofline. So more than likely those nails are going through the step flashing. Do you think that it could be leaking at those nail holes? The roof was replaced maybe ~15 years ago and I'm guessing the step flashing it at least that old (the home was built in 1993). Any advice would be much appreciated.

Here are some pics for reference.
https://photos.app.goo.gl/T75266fCvYzXahVy7

Thanks for the help!

is the weather watch 12" ,very siding j-channel/shingles is 6" underlay to metal aluminum 

The nails that they used to attach the j-channel are in the correct spot. Can not tell you where the leak is from the pictures you posted.

Would be nice to see pictures of the shingles and the siding in that area.