This error may appear if you are assigned a multimedia voice agent license and trying to put yourself in a "Ready" state.
IF your Chronicall configuration is set to show agents their skill group toggles, you will simply need to make sure you select at least one skill group before selecting the User Ready switch:
IF you do not see the skill group switches and only the User Ready switch, your Chronicall is likely configured to hide skill groups from the presence tool. A Manager, Admin, or Supervisor with proper Chronicall credentials will need to enable the agent into their skill groups in the Agent or Group Timeline. Please review this article for more details
If the agent should not be in any skill groups but you are seeing this message, you may remove the Multimedia Voice license from the agent in System Settings - Multimedia Voice - Multimedia Agents.