"This project cannot be opened in the Studio Edition you ar using"

I am working on a project and all of a sudden after closing it down I can't reopen it, and it has disappeared from my project list. The error message is "This project cannot be opened in the Studio Edition you are using. Only project packages or single documents can be opened." Can anyone please help? I have already tried to save the project locally on my computer instead of its usual location on One Drive but no luck.

Thank you!

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