Oh, my. That's part of the problem right there! As I typed the word conflict I realized that, yes, there's conflict, but it happens around the two main characters, not to them. In other words, there is Big Conflict, but no personal conflict.
That's why the writing is stalled. Personal and interpersonal conflict are the key ingredients and they're missing right now. I don't have any insights into what these personal and interpersonal sources of conflict should or will be. I just know I need to figure them out in order to truly begin this book.
And to think I thought my new tactic - rereading and creating a new "story bible" for the previous book - would be the thing to jumpstart my creative juices. If the sequel remained tightly focused on the hero and heroine of the first book, it might, but this new book only gives those characters a cameo appearance. So, while I may need to know some of the details the "story bible" will contain, it won't help me figure out what's going on with characters I've yet to fully introduce.
I love lightbulb moments. Especially unexpected ones.