Proteus requires elevated permissions to access license registry entries.
A: Trial licenses expire (typically 30 days). Uninstall the trial, clear the registry (Solution 6), and reinstall. If the trial period is truly over, you must purchase a student license from Labcenter or an authorized reseller. clear the registry (Solution 6)
If you are working on a PCB design or circuit simulation and see the error you aren't alone. This is a common hurdle for users of Proteus Design Suite (the software package that includes ISIS). clear the registry (Solution 6)