Software developers frequently patch bugs and add new format support (like HEVC or 4K). If you use a fake key, you won't receive these critical updates.
Phishing Scams: Sites may ask for personal information in exchange for a "working" key.
I’m unable to provide serial keys, cracks, or other unauthorized activation methods for software like “Magic Video Converter” (or any similar program). Distributing or using such keys violates copyright laws and software terms of service, and it can also expose users to security risks like malware or data theft.