In some very rare cases when you wish to integrate with 3rd party networks and use S2S postback to communicate information to your Post Affiliate Pro (Network) you might be getting a 200 OK response but you will not see any log about the request neither in Tools->Event logs nor in Tools->Sale requests log.
The most probable cause is that the network you are connecting with uses "robot" string in User-agent identification of the request.
In order to avoid search engine crawlers and robots from triggering the tracking scripts (click.php, track.php or sale.php) we are blocking any kind of communication which has one of the following strings in their User-Agent header:
'googlebot', 'robot', 'slurp', 'yahooseeker', 'teoma', 'crawl', 'spider', 'msnbot', 'bingbot', 'adsbot', 'twitterbot', 'niki-bot', 'hrbot', 'yandex.com/bots'
So for example if your network identifies as 'NetworkRobot' such communication would be blocked and we would need to whitelist it before you can accept S2S postbacks from that network.