
According to our official documentation, users with Teams Premium licenses can only view Project for the Web - Roadmap. To edit in Roadmap, users need an additional Project license.
"An appropriate Project subscription (Planner Plan 1, Planner and Project Plan 3, or Planner and Project Plan 5) is required for your Microsoft 365 or Office 365 users to create a Roadmap or a Project for the web plan. Users assigned with Microsoft 365 or Office 365 subscriptions are allowed to have basic edit access to projects that are shared with them without needing to be assigned a Project subscription. If your Microsoft 365 or Office 365 user needs to create projects or roadmaps, you'll need to purchase the appropriate Project subscription and assign it to the user. "
Please refer to Office 365 User access to Project for the web and Roadmap.
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