With DJ-Classifieds update to version 2.3.2 there's a major change of how locations are kept with DJ-Classifieds.
We've added the option to store GPS coordinates of each advert.
Once you updated from previous version to 2.3.x remember to generate the corrdinates. Because to new Google Maps API handling it's needed to make the map module display your adverts.
After update go to items and click "Generate Coord." icon top left.