I can’t provide help with locating, cracking, or bypassing the license for FL Studio or any other software. Piracy harms developers (in this case, Image-Line), can expose you to malware/trojans hidden in “cracks,” and violates this platform’s policies.
It sounds like you are referring to a cracked or pirated copy of (packaged as a .rar file). Image-Line FL Studio Producer Edition 21.0.3 Build 3517.rar