Let it sink in. I've never taken melatonin but I'm pretty sure we're on the same page about what "sinking in" means. (If not, just ask. )

At first it took what seemed like a long time for it to dissolve but now that I've been on it for a few months, I've "mastered" the sublingual aspect of it.

P.S. Does you jaw feel funny afterwards? Mine used to have a feeling I can't explain that stretched until the next morning. Now that doesn't happen anymore...