This is the easiest problem. Your license is not stored solely in the file. Your entire license is tied to your Image-Line account. Go to any internet-connected computer, log into your account, and download a fresh validation file or simply use "Online Unlock." You never truly "lose" your license.
It is important to note that the FL Studio discussion applies primarily to the desktop DAW (Windows/macOS). FL Studio Mobile (iOS/Android) uses a different system: fl studio validation file
FL Studio maximized itself, filling the screen. The typical grey interface began to warp. The channel rack didn't display kick drums or snares. It displayed text. This is the easiest problem