Symptoms

In the License Manager, the Activate License... button and the License > Activate... menu option are disabled and it is impossible to activate a license:

Cause

The issue would occur if the Licensing Service is not available or is not running.

Resolution

To confirm that there is an issue with the Licensing Service, the Refresh option can be used – the operation would fail with The RPC server is unavailable error.

The steps for resolving the issue are similar to the ones described here:

Application fails to run with the following error: ABBYY Licensing Service is unavailable. The RPC server is unavailable.