It sounds like you do not have the necessary permissions to publish a landing page. Permissions can be view, write, or publish:
You would have to reach out to a super admin in your portal, likely the person who invited you to HubSpot. If you do not remember, you can check under Settings > Users & Teams. They would have to update your permissions: https://knowledge.hubspot.com/settings/edit-user-permissions
Best regards!
Karsten Köhler HubSpot Freelancer | RevOps & CRM Consultant | Community Hall of Famer