Why do I get "Error 345" when trying to activate my MATLAB license?

When activating my MATLAB license, I get the following error:

 Error 345: We were unable to complete your request.  Contact MathWorks for assistance at <http://www.mathworks.com/support/contact_us/>

How do I activate my license?

Answer 1

[MathWorks Support Team]

This error indicates the activation key you are using is no longer valid. To complete activation, contact your license administrator or local IT department to obtain a valid activation key.