Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi Sim,
I can reproduce the same situation. The members will still need a "Project for Office" license to have basic edit access for Premium Planner plans. I'm afraid this is not a problem, but a normal situation. It's by design. The tenant admin needs to purchase or assign the relevant subscription to users.
Note that the "Project for Office" license is not equal to Project Plans (Project Plan 1, Project Plan 3, or Project Plan 5). "Project for Office" is included in Microsoft 365 for business, Microsoft F3, Microsoft E1, E3, and E5, giving users access to any functionality where Microsoft Project and Microsoft Planner for Web overlap.
For your reference:
Office 365 subscription with basic edit access
Appreciate your understanding and patience.
Sincerely,
George | Microsoft Community Moderator