If you can launch MATLAB:

If MATLAB is currently activated and able to launch, you can launch the MATLAB activation client from the MATLAB help menu:

In the "Home" section of the toolstrip, open the "Help" menu.
Hover over the "Licensing" submenu
Click "Update Current Licenses..."

If MATLAB will not launch:

If you have an expired or otherwise unusable license, MATLAB may not be able to launch. In this case, you will need to launch the MATLAB activation client directly.

Open Finder.
Go to "Applications".
Right-click or control-click on the MATLAB application icon. (e.g. MATLAB_R2017a.app)
Click on "Show Package Contents".
Open "Activate.app ".
Verify you are connected to the internet. Activate automatically using the Internet
Log in with a MathWorks Account and follow the online instructions.
1. Activation Key: 18162-63691-80459-26917-16111
When prompted to do so, select MATLAB (Designated Computer), click Next.
Click Next to complete activation.

Deactivate Matlab License

If the current license will not update, deactivating Matlab and re-licensing is needed.

To deactivate a license on your computer:

Start the deactivation application using any of the following methods.
1. Choose the deactivate option from the Help>Licensing menu in the MATLAB^®desktop.
2. On computers running Windows^® 10, go to MATLAB R2021a and open the folder. Right-click on MATLAB inside the folder, and select Deactivate.
Select the license that you want to deactivate and click Deactivate.
1. When the deactivation application starts, it displays the licenses you currently have installed and activated on your computer. If you start the application from within MATLAB, the license you are using is preselected.
Confirm deactivation. Click Yes and the deactivation application attempts to contact MathWorks.
Complete deactivation. Click OK.
1. If the deactivation application can deactivate the license on your computer and at MathWorks, it displays the Deactivation Complete dialog box. Click OK to return to the MathWorks Software Deactivation dialog box, where you can choose to deactivate other licenses.
2. If the deactivation application can deactivate the license on your computer but not in MathWorks systems, it displays the Deactivation Next Steps dialog box. This dialog box contains the deactivation string. To complete deactivation, go to the MathWorks website and log in to your account. In the License Center, deactivate the license using the deactivation string. Click OK to return to the MathWorks Software Deactivation dialog box.
After you deactivate a license, the MathWorks Software Deactivation dialog box displays an additional column listing the status of the licenses. Click Close to exit the deactivation application.

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