Hi , @jspwilli
According to my research, if you assign a free license to this guest user and your workspace does not assign any Premium capacity, this user can only manage and publish some content in "My workspace", this free version of Power BI option is for tenants and workspaces with Premium capacity, in the Premium capacity, free users can also access the content normally. However, if it is a shared capacity, you should consider assigning a Pro license to the user to activate the user's ability to view the shared content, so you can refer to this official document in detail:
Power BI: What's The Difference Between Desktop, Premium and Pro? (acuitytraining.co.uk)
For how to assign a liscense to a guest user , you can refer to this :
Assign licenses to users in the Microsoft 365 admin center - Microsoft 365 admin | Microsoft Learn
Purchase and assign Power BI Pro licenses - Power BI | Microsoft Learn
Thank you for your time and sharing, and thank you for your support and understanding of PowerBI!
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