Solved! Go to Solution.
You will need to request/download a new license that is good for Creo 8.
You may also need to update your installation of the licensing software.
If you installed a new license server that will let you run Creo 8, in order to run older versions of Creo I've been told that you need to use the "standard text" license file for the Flexlm software, not the other file that you were given. I think the file has the suffix ".std_txt".
Also, sometimes attempting to install different versions of Creo to run on the same system can break one of the installations, probably the last one installed is the one that works. I think it's a case of the last one installed setting the search paths in the environment so the older versions don't "see" their proper modules, etc. It can be pretty messy.
I just checked some old license files and the file name seems to be something like "lmxxxxxxx_standard.txt". Makes sense, I guess, since that will let you use standard text editors to open it by just clicking on the file.