Unsubscribing external users from workspace

Hi all

I have been testing allowing users external to the orgnaisation access to an app that I've built. There was an issue accessing but turns out it was a PowerBI general issue that's now been resolved. It was working fine and I can allow external teset users access but I wanted to try turning them off.

I get this error message when I do so however. Does anyone know how we're supposed to unsubscribe users?

I was in the edit workspace area and deleted that member by clicking the trash icon next to their name and then tried to save the settings when the above message box came up.

I need to make sure I can add and remove members with ease if PowerBI is going to work for my organisaiton.

thanks all!