Some Mac users are having problems using iSyncr over USB after the latest update to the HTC One. We can confirm that we are having issues with ours as well.

Using iSyncr over WiFi is going to be the easiest/best workaround. You can always setup WiFi to sync once a day at 3 a.m. like I do. This way it just happens and you always have your latest music and playlists.

Luckily for us, making a USB debugging connection was enough to keep syncing over USB.

However, I've found another guide on the web, if you are willing to root your device.

Please contact us if these methods do not work.