The RPL pdf add-on uses Google Maps' static service to show an image of where the property is located and since the pdf is generated on the fly and the php engine needs to be able to fetch the image from the Google Maps server, your server should be able to communicate with other servers and it is defined in a php parameter named "allow_url_fopen". If this parameter is set to "Off", your server cannot communicate with other servers and as a result, you cannot generate pdf flyers. You can check the status of this parameter either with your server provider or through the RPL back-end > Settings&Tools > Check & Maintenance under "Requirements".