(Individual and Campus-Wide license only) The username in the license file does not match
(Offline Activations) The Host ID in the license file does not match
(Designated Computer Only) MATLAB is already running under a different user account
Machine has a non-static Host ID

(Individual and Campus-Wide licenses only) The username in the license file does not match.

When installing or activating MATLAB, the MathWorks product installer or the activation client attempts to retrieve the username of the user installing MATLAB to activate. If the username was changed or the username retrieved is incorrect, the username in the license file will not match the username of the MATLAB user, and MATLAB issues License Manager Error -9.

To determine the username in the current session:

Windows: Open a command prompt and enter "set username"
Mac: Open a terminal window and type "whoami". Copy that result. You will need that at last step of the activation process.
Linux: Enter “whoami” in a terminal window.

To resolve, verify the username of the MATLAB user, and reactivate MATLAB with the correct username.

Note: Usernames are case sensitive and may not be recognized if they contain spaces.

(Offline Activations) The Host ID in the license file does not match.

When you activate MATLAB manually using the License Center, you must provide the Host ID, and for Individual Licenses, the username, to activate the license to the machine. If the wrong Host ID was used to activate, the Host ID in the license file will not match the Host ID on the machine, and MATLAB issues License Manager Error -9.

To resolve, verify the Host ID of the machine, and, for Individual licenses, the username of the MATLAB user, then reactivate MATLAB.

(Designated Computer Only) MATLAB is already running under a different user account.

With Designated Computer licenses, MATLAB may only be used by one user on one user account on the machine at a time. When MATLAB is started with a Designated Computer license, it attempts to detect any MATLAB processes already running on the machine. If there is a MATLAB process running under a different user account on the same machine, MATLAB issues License Manager Error -9.

To resolve, end all MATLAB processes on different user accounts on the same machine.

Non-static Host ID

For Individual and Designated Computer licenses, the Host ID used to activate MATLAB must not change over time or the Host ID will not match the Host ID in the license file, and MATLAB issues License Manager Error -9. This is common for many virtual machine configurations.

To resolve, configure your system to have a static Host ID, and then reactivate MATLAB.