My cofounder has suddenly ghosted me after working on a project together for nearly a year. We are near completion and launch of the first product (days away in fact). I havent heard from him in 3 days but he has logged onto social so he isn’t dead..

what you should do ?: contact him ! Go to his house with flowers, or ask a common friend of yours to find out what is the problem, ... - you know the situation better.

same happened to me. only heard from him once after a couple months. i didbanded the company as i had no other option and he owned half.