'License Key is Invalid' error when registering ReSharper (ReSharper 4.x - 8.x)

Currently, ReSharper license keys are mapped to the username, which was specified in the License Certificate e-mail. Please use the exact Username/License Key combination, as it is specified in the email (copy and paste is recommended).

Here is a common example, when wrong username (e.g., developer name) is used instead of correct one (e.g., Company Department name):