How to keep people more engaged in the server, like more engaged?

Hello everyone,

I an searching for tips how to keep people engaged on your server. 
Few days ago we had like an average of 2000 messages a day and now it is only around 500.

We have already seted up everything perfectly, we have events on the server, active admins/mods, we are active all the time reacting on people messages and posting our own content. But still people are not active/engaged in the server.

So if you have any tips on anything that could help please let me know.

Thanks!