We apologize that currently our TuneFab M4V Converter for Mac is incompatible with the macOS 10.13 High Sierra. But please understand that it is not just TuneFab, but all similar M4V Converters on the market are having the same situation.
The main reason for the incompatibility of High Sierra is that Apple has improved their system in the previous iTunes and Mac update. So we've made changes in the software accordingly to make sure that it can work with the latest iTunes and Mac system. If we can find a better solution later, we will update the software immediately. Please allow us some time.
If you have already purchased the TuneFab M4V Converter for Mac, we would like to give you the license key of TuneFab M4V Converter for Windows to keep enjoying the functions of converting iTunes Videos.