Can not sync apple tv

Just to be clear, unlike an iPhone or iPod, the ATV does not sync and transfer media from iTunes to itself.

It's only link to your iTunes account is the ability to directly stream purchased content associated with your iTunes account from Apple to it to view on demand.

Also you can set your iMac up as a server that the ATV can be made to connect to and stream content to the ATV again on demand.

Please describe your ATV version, see Identify your Apple TV model - Apple Supportand describe what you mean by "cannot connect".

Try disconnecting from iTunes from the Apple TV menu and then connecting again.