If you are on an enterprise plan, your enterprise plan has to have Adobe Video on the plan. Please contact your local Adobe administrator. If Firefly video is not on your enterprise plan, they can contact your organisation's Adobe account representative to enquire about adding it.
If you are on a personal plan, Adobe Firefly video is a premium service which requires a separate Firefly premium plan. For more information, please see the pinned reply in this post: P: Plan error in generating video.
If you are on a personal plan and have paid for a Firefly Premium plan, please post a screen shot of the error showing the full browser window including the avatar in the upper right corner.