If you are encountering 404 error pages when viewing classified listings, there are a few things that might be causing this. You should try the following in order:
- Ensure it is not a permalink issue by going to Settings > Permalinks from your WordPress dashboard and pressing the ‘save’ button
- Try disabling other installed plugins and then repeating (1). If it is a plugin conflict you can then either leave the problem plugin disabled or contact the author of that plugin.
- Switch to the default Twenty Sixteen theme to rule out a theme conflict, again repeating (1) after doing so.
By this point most problems should have been identified.