I have an occasional problem where people don't seem to realize I'm trying to communicate with them, but more frequently the problem is that after communication is already established, they have trouble understanding what I say. (Sometimes they act like they understood but didn't, sometimes they ask me to repeat myself a bunch.) I suspect the two are related.

I haven't found a solution, but I've been suspecting it's something autism-related. (I have subclinical "autistic traits" in other areas.) Something about having the wrong body language, wrong tone of voice, and/or wrong choice of words. By "wrong," I mean it's not what the intended recipient of your communication is subconsciously expecting.