Hi @William Wolfe ,
Great to know your issue is resolved and thanks for your sharing.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.", and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
Issue Symptom:
Can not add the Developer tab in PowerPoint ribbon.
The error message is as following image.
Issue Cause:
Auto_Save folder is added directly to Documents folder under user name folder, it should not be under the Documents folder linked to OneDrive.
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