I assuming you are on AEMaaCS where the Smart Tags is automatically provisioned OR you are using on premise and you have enabled this feature previously. If NOT, please refer to this guide: https://experienceleague.adobe.com/docs/experience-manager-learn/assets/metadata/image-smart-tags.ht...
On top of that, you need to "Enable Smart tag" feature from the asset folder properties.

If you have done this already, check the logs to see if there is any error.
Esteban Bustamante