ReSharper AI Assistant is not activated though the valid license key was specified

Problem

In the License Information window the license key is applied, but AI Assistant is shown as not activated ("AI assistant is not activated").

Cause

AI Assistant requires JB Account for activation.

Resolution

Enable Use JB Account option, press + button and login using your JB account.

Note: the following article also can be useful: Troubleshooting AI Assistant License-related issues for ReSharper.