What is the most logical next event?

How to confront someone who's giving you the silent treatment
Consider what else is happening in their life.
It could be that they're not actually giving you the cold shoulder. Maybe they, or someone they care about, is ill or having personal problems.
You won't know for sure until you ask them, but if you notice they seem more withdrawn with other people, too, it might not be the cold shoulder at all. If you notice a really severe personality change and other mutual friends do, too, talk to the person immediately.