Yesterday, Apple has released iTunes 12.1 version (http://support.apple.com/kb/DL1614). TuneChef Plus ( both Windows version and Mac version) supports the latest version of iTunes now, but if you are using the version 126.96.36.199 of iTunes, you will get the 20X faster conversion speed while removing DRM from M4V. However, if you updated to 12.1 and want to use v188.8.131.52 of the iTunes, you can uninstall iTunes 12.1 and re-install the old iTunes 12.0 version, also you can try TuneChef on another computer (installed the old iTunes 12.0.x version), this solution is better and easier so far.
How to uninstall and downgrade iTunes 12.1.x to 12.0.x
Go to the “Control Panel” – uninstall iTunes and related components> “Add or Remove Programs”
2), Apple Software Update
4), Apple Mobile Device Support
5), Apple Application Support (32-bit)
6), Apple Application Support (64-bit)
After that, you can install the Old iTunes, free download here:
Downgrade iTunes 12.1 to 12.0 Video Tutorial on YouTube
We are doing our best to solve this problem, thanks for your understand.