The Flexnet license key is only for Single User or Trial. Since you have a Floating Network license key, that must be setup on the Network/Server computer only.
Here's our Flexnet Installation guide, https://support.numericalinnovations.com/support/solutions/articles/14000026042-fab-3000-network-installation-setup-
Server Setup. First verify our vendor daemon "numinno.exe" is installed correctly on your Server. Steps #1-11 on our Flexnet Installation guide are specific to Server setup; please make sure you have followed each of them.
Note: Most companies already use Flexnet for other software, and will simply add our vendor daemon "numinno.exe" with license key,
If there is still a problem with the server running "numinno.exe", please generate a log file so we can determine what is occurring, https://support.numericalinnovations.com/support/solutions/articles/14000059931-flexnet-general-debugging-hints
You can also run diagnostics to help uncover any other potential problems, https://support.numericalinnovations.com/support/solutions/articles/14000059932-using-flexlm-diagnostics
Client Computer(s) Setup. Once you have determined the Server is working fine the next step is to establish the communication between the server and all client computer(s) that will be using FAB 3000. Essentially all you need to do on each client computer is add the environment variable NUMINNO_LICENSE_FILE, and determine the PORT# that will be used for communication between server and client.