Ask HN: How do you keep a physical community alive?

I'm a test lead in a medium large financial organization. As part of adopting SAFE (yes, i know...) and the Spotify model I am reviving a professional community under the COP or Guild hats respectively.

We have the basics- an ongoing leaders community, organizational support is expected, shared interest and problems to solve but somehow when I examine our history (and to be honest of other places as well) it seems that communities tend to be short lived.

I would appreciate any inputs or experience about keeping communities alive and bubbly over long periods.

This discussion [1] about online communities has some good tips, i wonder if virtual communities are that different than the ones in the real world

[1] https://news.ycombinator.com/item?id=21812442