Seems like something is wrong with the registry.
Please remove Typemock Isolator++.
Look for a registry folder: Computer\\HKEY_USERS\\S-1-5-21-3373439852-363486198-2619457599-XXXX\\Software\\Typemock\\ipp
(Note: The XXXX is 4 digit sequence which differs on every machine) and delete this folder.
Install and try to set the license again.
Please let me know if it solved the issue.