Hi,
Third party plugins are not guaranteed to work out of the box with Classipress due to its specialized function and will may require further code customization either to the theme or plugin to make them compatible. In the meant time, you can try looking for alternative plugins that does not cause some conflict.
Anyway, I am moving this thread to the Plugins Exchnage section for community support as there might be others who have used the plugin.
Cheers.
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Thank you and have a nice day.