Have you tried brainstorming about your main character? This is an exercise I teach in writing workshops and it seems to help get writers out of a rut. Basically, write down your main character’s first name and last name on a piece of paper. Do the same with a secondary character (could be someone they’re in conflict with). Then consider the following:
nickname? if yes, why? if not, why not?
what does this person love?
what do they want?
what bad habit do they have?
what do they eat for breakfast?
what kind of underwear to they wear?
where do they sleep?
what’s their job?
is there something everyone around knows them for?
Another idea is to get a job application form and try and fill it out for your characters. What all this does is expand your thoughts about your characters and think about them in a different way. Midway through the brainstorming your mind will explode with revelations. When that happens, think about how these two character confront each other, and then write that scene.
Remember that you don’t have to write your book in a linear way. You can start any place. Do this scene, and then write what comes before and comes after and eventually you’ll catch up to what you’ve already got.
I like to take my characters through a typical 24 hour day. Much of that ends in the trash heap, but again, doing this gives you revelations.
Also, think about your setting in a minute way. What the floor looks like. Are there bugs? What are the smells, touches.