Browse to C:\SIMULIA\EstProducts\202x\win_b64\SMA\site\EstablishedProductsConfig.ini and open it with a text editor:
Change dsls to flex in:
LICENSE_SERVER_TYPE=flex
and remove
DSLS_LICENSE_CONFIG=C:\ProgramData\DassaultSystemes\Licenses\DSLicSrv.txt
Add FLEX_LICENSE_CONFIG=<port>@<server name>
For example: 27000@myflexnetserver
Note: Flexnet can use ports between 27000-27009
Note: You can also use the server's IP address instead or name. e.g. 27000@75.83.76.202