Some antivirus programs are known to block the program’s attempts to save the activation data. Try to add the program to the exceptional rules of your antivirus or temporarily disable your antivirus software during the activation process.
In case of Avast antivirus you should disable its system service via Control Panel – Administration – System services during the activation process without reboot.
An easier way to solve this issue has been reported from our users. VPN Watcher may be successfully activated in Windows Safe Mode.