Your roofer is inept so you need a different roofer. Vet this one before hiring to make certain he know's the trade. Once the leaks are fixed,I would sue the origional roofer in small claims court for what 2nd roofer charged PLUS a dollar amount of damage caused to decking and ceilings.

Apparently no HOA on your attached townhouse, which I am guessing that is what you have. I wondered how that would work when you're physically attached to a neighbor and things go wrong because they could effect you.

I have a different roofer coming out on Monday. But can anyone tell what the problem might be from the pictures I posted? Thanks.

Really impossible to say from pictures, even more so as roofers have been unable to find the leak and they are looking at the roof in person.

Mill man is right but eventhough I can't tell you everything that's wrong from looking at the picture I can tell you the #1 rule of roofing has been violated. To believe what I'm about to say only requires going into an attic with Cedar shingles on a sunny day. You can see daylight hundreds of places but the roof doesn't leak. An even better example is found in poor communities of Asia where people use plants to cover their huts. As water run's down roof it should run off top of one surface onto the top of another surface INCLUDING when water seep's laterally as water always does. Now ,visualize water trikling down shingles adjacent to the so-called devider. When that water spread's/move's laterally,it go's UNDER instead of ONTO divider. Once beneath divider,there's nothing preventing it going through nail holes and seams of wood deck. No amount of tar,gup,caulk,silicone,poop or anything else will PERMINATLY prevent that. Conclusion. Devider should be laced or woven with shingles on both new and old roof. There are NO EXCEPTIONS to this rule.

Ok,eventhough I answered your question with everything you should need in my first response,you are still asking for in depth technical information. WHY? Do you believe you can learn enough to walk a roofer through the remedy? I'm serious and you owe me an answer to help me understand your line of reasoning. If you are thinking about becomeing a roofer,great,I'll engage as long as you like. If not,I give you a money back guaratee I will use what you tell me to better understand consumers and what make's them tick. In retirement,I furnish paid consultation to commercial and residential consumers and free consultation to indigents and agencies that serve them. I spend more time helping people steer clear of unqulified contractors and outright scammers than everything else combined. In your case I see a glaring problem from thousands of miles away,I'm pretty sure I could have told you the roofer is a dud if given an opertunity from 6 feet or on the phone.