Does this issue occur with all presentations?
I would like to suggest you create a new blank presenation to check this issue.
Did you make any changes to Office prior to this issue
Such as installing 3rd-party add-ins and updates.
Please click "PowerPoint" on top bar > About PowerPoint, check the version number and license name. Then take a screenshot and share with us. (If there is any privacy informaion like your email account, please remember to cover it.)
It's recommended to click View tab > Switch to Outline View > Clikc "Notes" option and click on "Click to add notes" for a test.
I also suggest you click "Tools" on top bar > PowerPoint Add-ins, temporarily disable add-ins.
Any updates, welcome to post back.
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