Hello Jim Hopkins,
Thank you for reaching out to Microsoft Q&A and informed us about the issue. After reviewing your issue, here's what you can do to reset your yubikey:
Option 1: Revert to Local account as suggested by Yubikey:
(Please do backup all of your important data before process since switching account can disable your syncing feature so be sure to backup all of crucial data first)
- Open Windows settings > Accounts > Your info > Sign in with a local account > follow the prompt and create a new username and password (Do remember the new password in case Yubikey fail) > then Windows will sign out and sign in to your new Local account
- Go to Windows settings > Accounts > Sign in options > Security key > Manage > add your Yubikey
Option 2: Reconfigure Yubikey:
- Open Windows settings > Accounts > sign-in options > look for Ways to sign in > Security key > Add > add your new Yubikey > follow the on-screen instruction
In case you don't want your sync to be interrupted, please consider to setup/use Windows Hello to login to your computer
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