See these links:
https://www.tenforums.com/tutorials/164857-how-fix-unable-add-use-pin-sign-option-windows-10-a.html
https://www.tenforums.com/tutorials/6518-remove-pin-your-account-windows-10-a.html
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Please remember to vote and to mark the replies as answers if they help.
On the bottom of each post there is:
Propose as answer = answered the question
On the left side of each post: Vote = a helpful post
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