What to do if I got license error when I try to simulate ModelSim in PC lab?
Close both Xilinx and ModelSim programs. Run the ModelSim Licensing Wizard. Leave the license path as default. After license is verify, you should be able to run ModelSim. For more information, check PartIV in the installation instructions. Q8: “Error: Cannot open library unisim at unisim.” (VHDL) See the solution at Xilinx Answer Database 10176. If this solution isn’t helpful, you may want to reinstall ModelSim. Make sure you remove previously install ModelSim before you reinstall it.