Unable delete Portfolios in Planner Premium

I am using Planner Premium under an institutional Microsoft 365 licence. Several Portfolios that I must have created at sometime, appear in my dashboard that I can't delete.  Not sure if they are linked to any planners as I get an error message:

“Something went wrong. We couldn't load the plans, please try again.”

Because the Plans list does not load, I am also unable to rename or delete the affected Portfolios. Refreshing the page and signing out/in again makes no difference.  Our institutional admin told me he can't help. 

Has anyone encountered this issue, and is there a way to remove or restore these Portfolios? Guidance would be appreciated.