Windows 7 handles MIDI differently. Go to Options > MIDI Settings. Under "Input," ensure your device is set to "Enabled" and "Send master sync" is turned OFF.

If you are looking to download this specific version, Image-Line maintains an official on their forums. This archive allows licensed users to access FL Studio 20.8.4 , the last true bridge between the modern era and the 32-bit legacy of Windows 7. Using FL Studio 64 Bit vs 32 Bit