Since FL Studio 11 is a legacy version, it is no longer hosted on the main product page. You must access it through the official archives:
Once installed, the software will run in until you unlock it with your license. FL Studio 11 Full Version Free Download
Where can I find older versions of FL Studio and their installers? Since FL Studio 11 is a legacy version,
: Download the latest available installer for version 11 (typically version 11.1 or the 32/64-bit unified installer). FL Studio 11 Full Version Free Download