OS X Server (Mountain Lion): "There was an error communicating with the remote content server" alert when starting the Caching service

Summary

Under certain conditions, you may see an alert when attempting to start OS X Server's Caching service:

"Unable to start service. There was an error communicating with the remote content server."

Products Affected

OS X Server (Mountain Lion)

Follow these steps:

  1. Check /Library/Server/Caching/Logs/Debug.log for messages containing the string "INVALID_DEVICE". An easy way to do this is by executing this command in Terminal:
    grep INVALID_DEVICE /Library/Server/Caching/Logs/Debug.log
  2. If you find messages containing the string "INVALID_DEVICE", reset your caching server's NVRAM by using the steps here.
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