I know of someone else who had the same problem, with ScannerCast, in the last 24 hours, including repeated-reboots after system-updates which did not solve the problem. Eventually, after all updates had been processed, the computer was rebooted, and allowed to idle for 10-15 minutes to clear-up any residual processes. Then ScannerCast was again restarted, and it worked. Unfortunately, the "exact solution" is not known; just that after repeated updates, and restarts, even after all updates seemed done, the feed finally returned.
Sometimes, the audio cable is the problem. If you haven't, you might try unplugging and reconnecting it.
Also, if the cable has been under strain, the wire might be broken internally at the base of the connectors. You might try to replace the audio cable, just to confirm/eliminate it as the problem.
Hope this helps,