SEO MotionZ Forum

I have started a new forum. I have got many members in a few weeks but after posting one or two times they are becoming inactive. And even some of them never posted in my forum. What should I do? Any suggestions.

Send them reminders, offer them various kind of free deals, help them, pm them personally, greet them in public occasions and also try to connect & engage with them in various social media channels.

Well I engage the inactive members my sending them weekly newsletters updates about my hot topics and most discussed & shared posts of my forum.