If your license is not recognized as valid, you can try the following workaround
If you receive an error message stating that you do not have a valid license for your Requisis software product, despite having a current valid license, please check if you started IBM Rational DOORS as an administrator.
When you start as an administrator, it sets different environment values and certain information can no longer be correctly read. This generates an error message that your valid license cannot be used.
Starting DOORS with the normal logged-in Windows user resolves the problem.