License key invalid; see long text

What causes this issue?

During the check, the program has established that the license key
entered is invalid.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Check the following:
Check whether the license key has been entered correctly, ensuring that
the correct capitalization is applied.
Ensure that you have entered the correct license key (and logged on with
the correct client).
Have you already contacted SAP concerning the migration (see SAP Note
812919)?
If you have excluded the above sources of error, contact SAP.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.