As examples, if trying to discover Sonos device(s) over the LAN using SSDP/mDNS multicasting and the device(s) cannot be discovered due to packet loss, device is asleep/powered off etc. then you may get a connection time out, or if you are attempting to play a music source and it’s either unavailable, or cannot be loaded to the queue within a set period (usually 15 seconds), or there is an issue with the source (unsupported bitrate, radio station has moved etc.) then you may also get a connection time out error too. 

Thank you!