I recall meetup.com having a search where you could search not just location but the thing of interest.
But now when I look at the site, it only has one search: by location.
What has happened to the search by topic option?
If you click on Where, then a box comes up and you can choose Where.
Once you have done that, then the search box works.
If you don't click the Where and enter a location, then the search doesn't work properly.
I have done another test. When the Where box hasn't been filled in then it either a)selects a location within 5 miles of my specific area and says "Within 5 miles of Blah". Or it just shows as 'Where'. So if for example, you are in a town within a large interconnected area such as London, then the default is it won't find much because it's just pulling info within 5 miles of your exact little town(when one might really want the 260ish locations easily accessible via london's train network). So you have to set that Where location (and to the bigger area - london, rather than letting it default to your little area and not find much.. either that or increase the radius). Prior to solving this I didn't realise that you could even click 'Where'.
Below is a pic of two windows, one where I didn't click and choose a location for Where, and one where I did.
As a test, I searched for NLP.
Click in the search box and you will get the topics and interests options.