For deactivation of a license via ABBYY License Manager you need to have a direct internet connection.  

To deactivate the license from ABBYY license manager, please do the following:

1. Open ABBYY  License Manager
2. Right-click on the serial number                                           ​
3. Choose "Deactivate..."
4. Follow the instructions of Wizard

Please note: 
This method is not suitable when the license has not allowed deactivation (typically licenses with limited page amount).

Online licenses cannot be deactivated locally.

In case that no direct Internet connection is available, the (on-premise) license file can be deleted from the Licences folder.

License files are named <SerialNumber>.ABBYY.License. This file is located in:  

ABBYY FineReader Engine 11: C:\ProgramData\ABBYY\SDK\11\Licenses

ABBYY FineReader Engine 12: C:\ProgramData\ABBYY\SDK\12\Licenses

ABBYY FlexiCapture 12: C:\ProgramData\ABBYY\FlexiCapture\12.0\Licenses

ABBYY FlexiCapture 11: C:\ProgramData\ABBYY\FlexiCapture\11.0\Licenses

After deleting license file, please restart the ABBYY Licensing Service and the ABBYY License Manager.