You're welcome. I've split this out into a topic of its own so that it doesn't get lost in the noise of the welcome thread.
That is incredibly common, and it means the value proposition is wrong. There is no compelling reason for people to come back. (Examples of compelling reasons are relationships/connecteness/strong sense of community at one end of the spectrum, and excellent content which invokes FOMO at the other.)
You get the above value prop right. Essentially you need to reconceptualise. In your case it sounds like you need to start from the beginning and work back up to critical mass. That will mean reaching out to a few members that are currently engaging, building really strong relationships with them, and getting them to form a small, highly engaged community which will model behaviour for the others. This will help.
Once the community is healthy, this will happen naturally. What platform is it on?
I'd archive it into a category somewhere so that you still leverage the SEO value but it's out of the way.
In the situation you're talking about – lots. Building (or rebuilding) a community is a full time job. Once you get the concept right and reach critical mass (as we have here) then you can step back. I manage this place part time (~10 hours per week).
The rest of the time I manage a community for community builders. You're welcome to join us – the questions you're asking here are the kinds of things we talk about full time.
And if you want a massive reading list of community resources, here's one.