There are already some good answers here, but none that really hit what you're after precisely. So I'm going to take a different tack, and suggest you might flop the subject and verb and say
I'm invisible to him.
This is a figurative usage, so you might add a qualifier:
Apparently I'm invisible to him.
Either way, it means he doesn't see you for whatever reason. It does not necessarily mean "he" is actively ignoring you, but it's likely to carry that connotation.
You might also try
He is unresponsive to me.
There can also be other reasons for his unresponsiveness, but this suggests you did make some effort to get his attention and failed.
As for coming up with an adjective that means exactly what you want in exactly the way you want it, I have cudgeled my brains for a while now and can't think of one. If I were trying to write a sentence with that meaning, I'd have given up looking for the exact word some time ago and simply recast the sentence to express my meaning another way.