Your Workfront account must be onboarded to the Admin Console and the “unified” login experience before you can use Planning.
This does affect your log in experience, which could require some communications prior to making the transition but if you want to expedite, you’ll have to contact support.
Adobe Workfront Planning trials require an active Select, Prime, or Ultimate plan, onboarding to the Adobe Unified Experience (IMS), and acceptance of the legal agreement by a system administrator between Jan 26 and April 1, 2026
https://experienceleague.adobe.com/en/docs/workfront/using/adobe-workfront-planning/adobe-workfront-planning-general-information/trial-workfront-planning#:~:text=Have%20any%20of%20the%20following,to%20accept%20the%20trial%20agreement.