Open SDL Trados Studio 2015 and in the Product Activation wizard, click Activate to display the Online Activation page.
Click Alternative activation options > Offline Activation:
Copy your activation code (located in Products & Plans > Licenses of your My SDL account) and paste it into the Activation code field. NOTE: The moment the activation code is placed in the field the Installation ID will be displayed:
Go to your My SDL account area in Products & Plans > Licenses locate your activation code and press on the right hand side: Can´t activate online? - Get an offline Activation Certificate
Copy & paste the Installation ID from the Production Activation dialog (see Step 3) into the Installation ID* field and press Generate Offline Activation Certificate
Copy the Activation Certificate:
Switch back to the Product Activation wizard and paste the Activation Code into the dialog using the Paste from the clipboard icon:
Click the Activate button. If the activation code is valid, the Activation Successful message is displayed.
Click OK. Your license has been successfully activated.
Open Studio and go to Help > Product Activation in SDL Trados Studio 2015.
Click Deactivate offline.
Login to your SDL Account > Products & Plans > Licenses.
Select your version of SDL Trados Studio 2015 and click Can't deactivate online? - Deactivate Offline.
In the Deactivation Authorization dialog box, copy the Deactivation Authorization Certificate:
Paste the Deactivation Authorization Certification into the Deactivation Authorization box and click Generate Certificate:
Click OK when you receive the message that the product has been deactivated locally.
Copy the Deactivation Certificate displaying in the Product Activation dialog.
Switch back to your SDL account and paste the Deactivation Certificate into the Deactivation Authorization box and click Deactivate. A confirmation page indicates the license has been successfully deactivated.
Switch back to the Product Activation Wizard, tick the box I have returned the deactivation certificate to SDL: