Retrieving Renewal License File
When your subscription renews with PTC, they will send you an automated email that looks something like the below picture. Of the 2 .TXT files that are attached, save the first lm_#####.txt - this is your renewal license file.
To reconfigure your FlexNet Server with the new license file, please see the how-to video from PTC (here).
To reconfigure a stand-alone locked instance of Creo, first navigate to the %(CREO_INSTALL_PATH)/Parametric/bin (see picture below) and select reconfigure.exe.
In the pop-up PTC Installation Assistant window, select the "Reconfigure Existing Software" and select Next. In the License page, remove the existing old license file (shown below) and upload the the new renewal license file. From there, you can click through and finish the setup - now you have the latest license file.