Do not confuse your FL Studio Mobile purchase with a desktop license. A mobile validation file does not exist, and a desktop validation file will not unlock the mobile app.
Image-Line has been gradually moving toward a more seamless online validation system. FL Studio 21 introduced the ability to stay validated via your Image-Line account without ever handling a .reg file. fl studio validation file
Depending on your version of FL Studio (20, 21, 2024, etc.), the validation file may appear under several names: Do not confuse your FL Studio Mobile purchase
~/Library/Application Support/Image-Line/FL Studio/ fl studio validation file
The file was accidentally deleted during a cleanup (using CCleaner, for example) or the ProgramData folder was cleared. Also happens when restoring from a backup that excluded hidden system folders.