Either your firewall has started blocking Poser's internal communication, or you have another application running first which has stolen the required TCP port.

What has changed? Did you install any software? Did you do any updates? Did you change firewall values? Were you presented with a dialog asking permission to let Poser do something and you answered No?

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)