You can get the error message if —

You are trying to activate a TestComplete trial license on your computer while another trial license is already activated on this computer.

TestComplete displays this message to inform you that the new trial license cannot be activated on this computer. You can activate a TestComplete trial license only once on a computer. After the trial period expires, you cannot continue working with the product activated with the trial license key. To use the product, you can either purchase the needed TestComplete license and activate it or you can upgrade the existing trial version to the commercial version during the trial period. For detailed instructions on upgrading from the trial version, see Updating TestComplete Trial Version to Commercial Version.
You are trying to activate the emergency license for the 25th time on this machine.

TestComplete displays this message to inform you that the emergency license cannot be activated more than 24 times on the same machine.

You can also try resolving the problem by using the Licensing Troubleshooter on our web site:

Unable to Active the License on This Machine, Because Another Trial License for the Product Has Already Been Activated on It