iMac no longer finds the iPod Touch (or any other iDevice).

The app was working fine between my iPad, iPod Touch and the iMac yesterday. On first try today the iMac found the iPod, but could not transfer, now it cannot find any device. All are on my home Wifi which I have reset. I also reloaded the app in the iPod and the iMac. I shut down the iMac and restarted...still no luck. Any suggestions?