This post is meant to help customers that are having issues with licensing on Android 3.0 and later.
First, make sure you are using iSyncr 2.6.3 or later. This version of iSyncr reduces the chance of seeing this error. If you are using iSyncr 2.6.3 or later, read-on.
Background (Optional): Starting in Android 3.0, Android devices use "MTP" instead of "Mass Storage" for sending files over USB. This is an improvement in security and file integrity. However, it is not a speed improvement and it does have more software behind it that has to be maintained. As a result, sometimes customers see a "license missing" error from iSyncr. This a result of Android's MTP implementation not being seasoned yet. We have filed bugs with the Android Open Source Project about this (early in 2011).