The sound servers do seem to be a bit unreliable at times.
Although I don't have the dodgy problem Chrono has, fix your own system 
However, if you are never able to send or receive any sound at all even when you tried at a few different times, something else might be the problem. Can you access
http://sounds.msgpluslive.net/ in your browser? Sounds are downloaded by Plus! internally from that location. If something is preventing connection to that server that will explain why sounds aren't playing. It could be due a firewall or some kind of security application. For example, up until 2 days ago MalwareBytes was blocking the IP addresss of the sound servers.
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